the new guinea big-eared bat ( pharotis imogene ) is a vesper bat endemic to papua new guinea .

it is listed as a critically endangered species due to ongoing habitat loss .

it is the only known member of the genus pharotis , which is closely related to nyctophilus .

previously , the species was believed to have been extinct since 1890 , when it was last spotted .

in 2012 , researchers realised that a female bat collected near kamali was a member of this species.due to its imperiled status , it is identified by the alliance for zero extinction as a species in danger of imminent extinction .

in 2013 , bat conservation international listed this species as one of the 35 species of its worldwide priority list of conservation .

new guinea big - eared bat

new guinea big - eared bat <EOT> back after going missing for more than a century : the new guinea big - eared bat .

in march 2014 the bat was loaned to the australian museum in sydney , where researcher harry parnaby identified it as pharotis imogene – the new guinea big - eared bat .

this article was co - authored by catherine hughes . the new guinea big - eared bat was rediscovered as part of her honours project at the university of queensland .

more than a century after it was “lost” , the new guinea big - eared bat has been discovered by queensland researchers working in papua new guinea’s forests . the critically endangered bat was thought to be extinct , and the discovery shows there is still much to learn about biodiversity in our region .

the new guinea big - eared bat ( pharotis imogene ) , is a species of vesper bat endemic to papua new guinea . it is listed as a critically endangered species due to ongoing habitat loss . it is the only known member of the genus pharotis , which is closely related to nyctophilus .

the new guinea big - eared bat , like the rest of the genera pharotis and nyctophilus , is distinguished by a combination of two features : large ears and a simple “nose - leaf” structure immediately behind the nostrils . collectively , the group of species is known as long - eared ( or big - eared ) bats . p . imogene has larger ears than most .

scientists in australia are walking back their presumption that the new guinea big - eared bat ( pharotis imogene ) - - a species of bat last spotted in 1890 - - was lost . field researchers recently realized that one of the specimens they collected during an expedition to papua new guinea in 2012 was none other than the supposedly extinct bat , which has not been seen in more than 120 years .

in a study published last week , the team described how it was able to identify the specimen as the presumed extinct new guinea big - eared bat . though the winged creature was initially thought to be a small - toothed bat , which also has characteristically large ears and a leaf - like nose structure , comparative material allowed researchers to confirm that the specimen is the pharotis imogene . ( the first and - - until now - - only specimens of the new guinea big - eared bat were reportedly collected by an italian scientist in 1890 . )

when catherine and julie captured their bat , on the edge of logged forest near an old coconut plantation now covered with grassland , they thought it was either the small - toothed nyctophilus ( nyctophilus microdon ) or a pharotis – the genus to which the new guinea big - eared bat belongs .

now that the long - lost species has been rediscovered , so to speak , researchers are seeking to determine how the big - eared bat remained hidden for more than 120 years .

the new guinea big - eared bat pharotis imogene has not been reported since the first and only specimens were collected in 1890 and the species was presumed extinct . we document the capture of one individual of the species from the coastal district of abau , in central province , papua new guinea , 120 km east of the only previous known locality at kamali . we recommend that field surveys be urgently undertaken to assess the conservation status of the species .

— this is a list of the mammal species recorded in papua new guinea . there are 242 mammal species in papua new guinea , of which 7 are critically endangered , 12 are endangered , 39 are vulnerable , and 0 are near threatened . [ this list is derived from …

— this is a list of the bird species recorded in papua new guinea . the avifauna of papua new guinea includes a total of 781 species , of which 76 are endemic , one has been introduced by humans , and 18 are rare or accidental . 28 species are globally… …

new species of mammals from northern south america : a long - tongued bat , genus anoura gray .

nothing is known of the ecology of new guinea big - eared bat , and therefore more surveys are needed in the coastal lowland rainforests of southern png . many lowland rainforest habitats are being disturbed by timber logging ( both sustainable and otherwise ) , clearing for development , and agriculture . the effect of these disturbances on the bat is unknown ; however if the species is found in low numbers , it may be threatened by local disturbances .

researchers recommended further field studies in order to evaluate the conservation status of the species . as the conversation notes , timber logging in lowland rainforest areas on the island could potentially disturb the big - eared bat ' s habitat , if the population is relatively low .

a third geographic region where bat - catching by web - building spiders was repeatedly witnessed ( seven reports ) is the area of australia ( report # 39–44 ) and papua new guinea ( report # 45 ) . most australian incidences were observed in the coastal areas of new south wales and queensland (

as the authors note in a may 30 article for the conversation , much of lowland papua new guinea ' s rainforests are being cut down for timber or to make way for development or agriculture . that practice could place additional pressures on the big - eared bats as well as other microbats in the region . in other words , we may not have another 120 years to save this rediscovered species .

this research was undertaken with permission from the national research institute , papua new guinea , who organised the research visa to conduct field research in cloudy bay , abau , central province , papua new guinea . this work was conducted under animal ethics approval , granted from the university of queensland animal ethics committee number : safs / 165 / 11 / various funds

might be less efficient in bat catching . the only reported incidence where a bat got entangled in a

— taxobox name = big eared flying fox status = lr / lc | status system = iucn2 . 3 regnum = animalia phylum = chordata classis = mammalia ordo = chiroptera familia = pteropodidae genus = pteropus species = p . macrotis binomial = pteropus macrotis… …

3 new species of weird , endangered fish discovered in india , u . s and colombia

on july 25 , 2012 , catherine hughes and julie broken - brow caught a small , female bat in a trap at the edge of a forest in southeast papua new guinea ( png ) . but the bat didn’t match any species known to exist . and so began a fascinating detective story about a species that hadn’t been spotted for more than 120 years .

churchill s ( 2008 ) australian bats , 2 nd edition . sydney : new holland . 255 p .

griffin dr ( 1958 ) listening in the dark . new haven : yale university press . 413 p .

of course , conclusively identifying a species that hasn ' t been seen in 124 years is no easy task , especially when ( as in this case ) the only previously known sample used to describe it has long since disappeared . as recounted in the may 28 issue of records of the australian museum , parnaby was able to distinguish the rediscovered bat from other species by the curve of its nose , the size and lobes of its ears and the naked skin above its nostrils . other than these relatively minor physical attributes the pharotis bat looks quite similar to another local species , the small - toothed long - eared bat ( nyctophilus microdon ) . in fact , a specimen from this species was found in 1985 and initially misidentified as the big - eared bat until it was reexamined three years later .

sometimes research into one question reveals the answer to another . in july 2012 catherine hughes and julie broken - brow , students at the university of queensland in australia , were in papua new guinea studying how the region’s tiny microbats responded to sustainable logging of their forest homes .

gertsch wj ( 1979 ) american spiders , 2 nd edition . new york : van nostrand reinhold . 196 p .

marshall sd ( 2001 ) tarantulas and other arachnids . hauppauge , new york : barron’s educational series , inc . 111 p .

pp . 151–200 in ecology of bats ( t . h . kunz , ed . ) . plenum publishing corporation , new york

lunar phobia in a neotropical fruit bat , artibeus jamaicensis ( chiroptera : phyllostomidae ) .

collected by queensland students catherine hughes and julie broken - brow in july 2012 , the female bat was euthanized and held at the papua new guinea national museum and art gallery for future research . then , nearly two years later , harry parnaby , a research associate from the australian museum , received the specimen on loan so he could determine the species , according to australian news website the conversation .

leen n , novick a ( 1969 ) the world of bats . new york : holt , rinehart and winston . 171 p .

allen gm ( 2004 ) bats : biology , behavior , and folklore . new york : dover publications , inc . 368 p .

sometimes research into one question reveals the answer to another . in july 2012 catherine hughes and julie broken - brow , students at the university of queensland in australia , were in papua new guinea studying how the region ' s tiny microbats responded to sustainable logging of their forest homes . as part of the project , the scientists trapped and caught 41 bats from nine known species—as well as a female bat they could not immediately identify .

field rate of metabolisms and water uptake in the blossom - bat syconycteris australis ( megachiroptera ) .

— for other uses , see bat ( disambiguation ) . bats temporal range : 52–0 ma …

now that p . imogene has been rediscovered , the authors note that much remains to be learned about it . part of hughes and broken - brow ' s original work involved recording the echolocation calls of papua new guinea ' s bats . we still don ' t know what the big - eared bats sound like nor do we know anything about their ecology . what are their habitat requirements ? what do they eat ? how and where do they nest ? how many of these rare bats remain ? the authors wrote that " detailed surveys are needed to critically determine whether this species requires the proximity of both rainforest and more open habitats , " which would help to determine regional forestry practices . they also note that earlier surveys of protected areas have never turned up any sign of this species . the bat was found in an unprotected area , so its habitats may be at risk . they recommend new surveys to establish the bat ' s distribution and abundance , additional acoustic studies to see if its echolocation calls can be identified and ( if anyone gets that far ) radio surveys to define their habitat and roosting requirements at various stages of their reproductive cycle .

habitat exploitation by a gleaning bat , plecotus auritus . philosophical transactions of the royal society london , b

seasonal changes in energetics and torpor patterns in the subtropical blossom - bat syconycteris australis ( megachiroptera ) .

this species has not been recorded from any protected areas . field surveys using appropriate sampling techniques ( e . g . , harp traps ) are urgently needed to determine if this species is still extant . this is one of the highest priorities for surveys in papua new guinea ( f . bonaccorso pers . comm . ) . any important roosting or foraging sites should be protected .

measurements of the new specimen are consistent with those of the first specimens collected in 1890 from a coastal village called kamali , 120 km west of our study site .

whitaker jo , hamilton wj ( 1998 ) mammals of the eastern united states , 3 rd edition . ithaca , new york : cornell university press . 608 p .

fresh weight and wingspan of bat species reported to be captured by spiders ( arranged in alphabethical order ) .

the trap that caught the bat was only at the site for two nights , making this discovery particularly lucky .

heterothermy and the use of torpor by the bat eptesicus fuscus ( chiroptera : vespertilionidae ) : a field study .

pp . 11–45 in high altitude tropical biogeography ( f . vuilleumier and m . monasterio , eds . ) . oxford university press and american museum of natural history , new york

- have been reported so far to be engaged in bat catching . it can be assumed , however , that other

justification : listed as critically endangered ( possibly extinct ) because if this species still exists it is likely to have a very small population size , and small range size that is subject to a continued decline in extent of occurrence , area of occupancy , and the extent and quality of habitat . this species has not been recorded in more than 100 years ( since 1890 ) and it is known only from a rapidly changing portion of southeastern papua new guinea . there is still a possibility that new survey methods to the region , particularly harp traps , might lead to the rediscovery of this species and such surveys are urgently needed .

temperature regulation , rate of metabolism , and roost temperature in the greater white - lined bat saccopteryx bilineata ( emballonuridae ) .

fifty - two reports of bat - catching spiders based on literature and unpublished data ( for more details see file s1 ) .

the roles of energetics , water economy , foraging behavior , and geothermal refugia in the distribution of the bat , macrotus californicus .

it is the first record of the species since 1890 – meaning that this bat was missing in action for the entire 20th century .

resource and habitat use in two frugivorous bat species ( phyllostomidae : carollia perspicillata and c . castanea ) in panama : mechanisms of coexistence

foraging mode and echolocation call frequency of adult bat species reported to be captured in spider webs ( arranged in order of increasing peak frequency ) .

pp . 39–47 in biology of bats of the new world family phyllostomatidae . part i ( r . j . baker , j . k . jones , jr . , and d . c . carter , eds . )

care and management of the long - tongued bat , glossophaga soricina ( chiroptera , phyllostomatidae ) in the laboratory , with observation on estivation induced by food deprivation .

in 2013 , a rapid biodiversity survey conducted by the wildlife conservation society in a remote location of png ( hindenburg wall ) discovered at least 89 new plant and animal species . these surveys show that png’s biodiversity numbers will continue to grow as we survey more of the country .

was observed eating a bat on the forest floor in northeastern brazil ( r . west , pers . comm . ; report # 3 ) . moreover , a large reddish parachute tarantula ,

; report # 11 ) , the captured bat might have been a juvenile fruit - eating phyllostomid bat though the features needed for a positive identification were not sufficiently recognizable in the photo ( a . gardner , pers . comm . ) . the old world flying foxes ( pteropodidae ) have never been reported to get captured or killed by spiders except for one report from captivity . liat

; g . jones , pers . comm . ) . one might expect such highly specialized foragers to be sufficiently well adapted to avoid collisions with spider webs . however , studies in new south wales ( australia ) and bavaria ( germany ) revealed that gleaning insectivorous bats ( i . e . ,

, may 2011 ) . another incidence of a bat caught in a spider web was observed on the isle of wight , south east england ( g . street , pers . comm . ) .

deaths of bats in spider webs have been considered to occur very rarely . in two more recent papers , a web - building spider , argiope savignyi , and a theraphosid spider , poecilotheria rufilata , were each reported to predate on a small bat [ 30 ] – [ 31 ] . these authors hypothesized that bat captures and kills due to spiders might be more frequent than previously thought . to test this hypothesis , an extensive global literature survey on bat - catching spiders was conducted , along with an attempt to use web - based sources as well . the insights from this research are reviewed here .

previously , the species was believed to have been extinct since 1890 , when it was last spotted . in 2012 , researchers realized that a female bat collected near kamali was a member of this species .

an extensive bibliographic search was conducted in order to find any information available on bat - catching spiders . the search was based largely on the thomson - reuters data base ( web of science ) , google scholar , google books , proquest dissertations & theses , and flickr image - hosting website ( hosting more than 6 billion images ) . in addition to this , an internet search for blogger information on this topic was conducted . bloggers who had posted photographs and reports on bat - catching spiders on the internet were contacted to get detailed information on their observations . furthermore , the staff of bat hospitals was contacted to get information on bats rescued from spider webs . finally , an inquiry among fellow arachnologists and chiropterologists was carried out to get access to unpublished reports on this topic . many of these experts had conducted field studies for decades , and their feedback provided valuable information needed to assess how frequent incidences of bat catches by spiders might be . altogether , 52 reports on bat - catching spiders could be gathered (

threlfall c ( 2011 ) conserving biodiversity in urban landscapes . mechanisms influencing the distribution , community assembly and resource use of insectivorous bats in sydney , australia . ph . d . thesis , evolution & ecology research centre , school of biological , earth and environmental sciences , university of new south wales , sydney , australia .

web ended with the bat’s successful escape . nevertheless this spider species should not be ruled out as a potential predator of small bats ; it is known to catch and eat various types of vertebrates including small birds

in general , moderate spatial overlap occurred between the foraging and core areas of individual bats ( fig . 2 ) , which were distributed along the lakeshore in bat cove , at fairchild and harvard peninsula , and around colorado point . during some nights 1 female ( f3 ) crossed the canal and spent part of the night foraging somewhere around the mainland peninsula buena vista . this individual thus had at least 1 other foraging area , the exact location of which could not be determined because we were not able to continuously follow this bat and obtain a sufficient number of radiofixes within that area . bat f5 had by far the largest home range and its foraging areas were located far from one another . during some tracking nights we lost contact with the bat as it moved quickly out of the range of the receivers . on 1 night , we managed to follow this bat as it traveled about 7 . 5 km from the day roost along the barro colorado island shoreline to another foraging area located around gigante , a nearby mainland peninsula ( fig . 2f ) .

the bat was ethically euthanized and taken to the png national museum and art gallery in port moresby . specimens like this are an important reference for future research , and also a good way to identify species whose identity cannot be confirmed in the field .

to facilitate comparison with other studies , we used 95 % kernel isopleths to delineate foraging areas ( white and garrot 1990 ) . in contrast to the home range , foraging areas do not include the day roost and areas traversed by a bat while commuting .

bat - catching spiders belong to the araneomorph families nephilidae ( golden silk orb - weavers ) , araneidae ( orb - weaver spiders ) , sparassidae ( huntsman spiders ) , and the mygalomorph family theraphosidae ( tarantulas ) . furthermore , an attack attempt by an araneomorph hunting spider of the family pisauridae ( fishing spiders ) was witnessed . seventy - three percent of the known incidences of bat catches were attributable to orb - weaving spiders , 15 % to unidentified web - building spiders , and 12 % to hunting spiders (

a second geographic region where bat - catching by web - building spiders has frequently been reported ( 13 reports ; 2i and l ) is eastern and southeastern asia including locations in china ( report # 26–34 ) , japan ( report # 35 ) , vietnam ( report # 36 ) , malaysia ( report # 37 ) , and sri lanka ( report # 38 ) . here , bat - catching by spiders have been witnessed particularly often in the eastern coastal area of china , specifically in parks and forests of the greater hong kong area (

we further identified number and locations of foraging and core areas of each tracked individual and calculated the distances a bat traveled on a nightly basis within its range to describe patterns of range use . specifically , we calculated the minimum distance flown per night ( based on the distance between successive fixes ) , as well as maximum range span , that is , the distance between the day roost and the farthest point of a bat ' s home range . moreover , we quantified the distances the bats traveled when commuting from the day roost to the nearest foraging area .

in the bat communities of andean cloud forests , frugivores represent the most species - rich guild , in contrast with lowland rain forest bat communities , where insectivores are the dominant guild ( fleming 1986 ; graham 1983 ; patterson et al . 1996 ; soriano 2000 ; soriano et al . 1999 ) . apparently , insectivores of tropical origin have a limit to their vertical distribution that prevents them from accessing andean cloud forests , and only some vespertilionidae of neartic origin reach these forests , along with a few representatives of the molossidae ( soriano 2000 ; soriano et al . 1999 ) .

with regard to bat - eating theraphosids photographed in the neotropics and in india , the actual killing of the bats was not witnessed . however , it has been proven by means of observations in captivity that large theraphosids are capable of killing bats . this is shown in a youtube video where a

the neotropical orb - weaving spider eriophora fuliginea has been observed to kill and eat small bats that got entangled in its webs [ 8 ] , [ 37 ] , [ 101 ] . when a bat got caught in a web , the spider immobilized the bat by attack - wrapping and subsequently biting it [ 101 ] . following this , the spiders fed on the dead bats for many hours ( d . e . wilson , pers . comm . ) . the incidences of bats being caught , killed , and eaten in webs of eriophora spp . are without any doubt predation events .

png is one of the world’s biodiversity hotspots . the country accounts for about 7 % of the world’s species diversity , with about 276 known mammal species , 314 freshwater fish , 641 amphibian and reptile species , 740 birds , and many more . according to the world wildlife fund , between 1998 and 2008 , 1060 new species were discovered , including a blue - eyed spotted cuscus , a 2 . 5 metre freshwater shark , and a giant bent - toed gecko .

) : vespertilionidae ( plain - faced bats ) , emballonuridae ( sheath - tailed bats ) , rhinolophidae ( horseshoe bats ) , hipposideridae ( old world leaf - nosed bats ) and phyllostomidae ( new world leaf - nosed bats ) . in 31 % of the reported incidences the captured bats remained unidentified . the majority of identifiable captured bats belonged to the families vespertilionidae ( 64 % of reports ) or emabllonuridae ( 22 % ) , whereas only few reports existed for hipposideridae ( 8 % ) and one for rhinolophidae ( 3 % ) . the capture of phyllostomid bats was only reported once ( report # 20 ) or maybe twice ( report # 11 ) . in the latter , uncertain report , concerning a small brown - coloured bat entangled in a spider web in guatemala (

during these inquiries we got access to several previously unpublished photographs of bat - catching spiders . these photographs were shown to established bat and spider taxonomists for identification of the bats and spiders , respectively . in a few cases photographs of habitats were sent to vegetation specialists for proper habitat classification . nomenclature follows [ 32 ] – [ 33 ] . spiders reported in this paper are divided into two major groups based on foraging mode ( sensu gertsch [ 14 ] ) : “hunting spiders” ( i . e . , spiders that forage without the use of a catching web ) and “web - building spiders” ( i . e . , spiders that forage using a catching web ) . data on spider weight and size as well as bat weight , wingspan , foraging mode and echolocation call frequency were taken from the literature when available . report numbers used in the results , tables and figures refer to the respective detailed report description ( see file s1 ) .

with about 150 species , new world leaf - nosed bats ( phyllostomidae ) are dominant components of local bat faunas in neotropical lowland forests . phyllostomid bats are ecologically highly diverse and unparalleled in their feeding habits , exploiting a wide selection of foods , ranging from fruit , leaves , nectar , and pollen to insects and other arthropods , small vertebrates , and blood ( e . g . , findley 1993 ; kalko et al . 1996 ) . although radiotracking studies have long focused on frugivorous members of this speciose family ( charles - dominique 1991 ; fleming 1988 ; handley et al . 1991 ; heithaus et al . 1975 ; morrison 1978 ; thies 1998 ) , insectivorous species have just started to receive some attention ( bernard and fenton 2003 ; kalko et al . 1999 ; weinbeer and kalko 2004 ) .

consumption reached a minimum level at least once , the bat was taken from the chamber , body temperature was measured with a rapid - read thermometer , and body mass was measured . rate of metabolism , as determined by rate of oxygen consumption , was calculated and expressed as a mass - specific rate with the equation of

energetic variables reported for bat species with different diets and from lowland and montane habitats . actual values measured are compared with predicted values ( as percentages of predicted ) . for bascal metabolic rate , predicted value is from mcnab ( 1988 ) , and for thermal conductance , predicted value is from herreid and kessel ( 1967 )

( pisauridae ) to kill a bat pup has been witnessed below a bridge in indiana , usa ( p . clem & v . brack , pers . comm . ; report # 6 ) . however , in this latter case the predation attempt failed probably because the spider was frightened by the presence of the photographing observers ( see

; report # 49–50 ) , and these both refer to warm areas in the southern usa . incidences of bat catches by orb - weaving spiders are unknown from the northern part of north america ( b . fenton , pers . comm . ) . likewise , incidences of this type have not been reported in the ukrainian and russian scientific literature ( a . t . bashta , pers . comm . ) . only two incidences of bats being captured in spider webs have been reported from europe ( report # 51–52 ) . in one case , a dead bat was found entangled in the web of an orb - weaving spider on a building site near stuttgart , germany ( german tabloid

field observations . —occasionally we were able to follow a bat ' s flight path with a flashlight by illuminating the reflecting tape attached to the transmitter . characteristically , the bats foraged at low heights ( < 50 cm ) above the water surface , either flying under or close to overhanging vegetation along the shore but they often also ventured out several tens of meters onto the lake . in general , however , most bats hunted within 50 m from shore . in this context , 1 female ( f4 ) again was a notable exception because examination of our tracking data indicates that this bat periodically foraged at large distances , sometimes as far as 600 m , away from shore out on the lake .

the purpose of this paper is to examine adaptive responses of 3 bat species with different food habits ; responses , which the species use to solve problems of survival and energy balance in neotropical high mountains . thus , we will take into account theoretical aspects of metabolism and temperature regulation to characterize physiological features that distinguish some species that are capable of living in such environments .

in temperate latitudes , the vespertilionid bat eptesicus fuscus uses facultative daily torpor linked to environmental and reproductive conditions ( audet and fenton 1988 ) . however , the cost of this mechanism in pregnant females is prolonged gestation . characteristics shown by e . fuscus possibly occur in tropical montane representatives of the vespertilionidae , permitting this family to have a higher representation than molossidae in tropical cloud forests .

in this paper we test the hypothesis that bats of the andean highlands show distinctive metabolic responses compared with bats from lowland forests . we compared existing literature with new information on 3 bat species having the following food habits : a nectarivore ( anoura latidens ) , a frugivore ( sturnira erythromos ) , and an insectivore ( tadarida brasiliensis ) . basal metabolic rate , as determined by oxygen consumption , thermal conductance , and body temperature were measured at ambient temperatures of 10–38°c . some distinctive metabolic responses of these bat species , although varying with respect to food guild , allow us to separate them from counterpart species that are typically found in lowland forests . a . latidens is characterized by higher basal metabolic rate ; however , thermal conductance and lower critical temperature values do not show an adaptation to cool environments , as expected . s . erythromos also increases its basal metabolic rate , but it maintains thermal conductance as expected , which implies a very important displacement of thermoneutral zone to lower temperatures . at temperatures below lower critical temperature , in addition to an endothermic response , s . erythromos sometimes expresses a hypothermic response or facultative torpor , independent of sex and body mass . t . brasiliensis has a lower basal metabolic rate and thermal conductance and also has its thermoneutral zone range displaced toward lower temperatures . likewise , this species enters obligate torpor when ambient temperatures are below 22°c .

although available information is yet very limited , there is evidence to support the hypothesis that thermoregulatory restrictions prevent some species of bats from inhabiting high mountain environments . this includes the tendency for metabolic rate , minimal thermal conductance , and lower critical temperature in some bat species in andean cloud forests to vary with food habits . qualitative and quantitative differences separate andean mountain bats from those of lowland forests .

— bat1 / bat / , n . , v . , batted , batting . n . 1 . sports . a . the wooden club used in certain games , as baseball and cricket , to strike the ball . b . a racket , esp . one used in badminton or table tennis . c . a whip used by a jockey . d . the act of using a… …

) , body temperature , and thermal conductance were measured . although temperature intervals were not the same for each species , the experiments were done at ambient temperatures between 10 and 38°c . measurements were taken in an open - flow respirometer using the following protocol : the bat was placed in an hermetic metabolic chamber of 450 ml with mesh plastic walls and roof to allow it to rest in a normal position . a sufficient quantity of lead bullets was put at the bottom of the chamber to permit submersion in a thermally controlled bath . ambient temperatures inside the metabolic chamber were measured by thermocouples connected to a hh23 microprocessor digital thermometer ( omega , stamford , connecticut ) . air was pumped from the room through the chamber , maintaining an air flow of 70–80 ml / min , measured by a matheson 601 rotameter ( secaucus , new jersey ) . to ensure adequate mixing of air in the chamber , incoming and outgoing air tubes were placed at different levels . outgoing air flowed through a column of indicating silica gel to dehydrate it , through another column of indicating soda lime that absorbed co

yet at the same time , major losses to png’s biodiversity are being caused by rapid human population growth , forest degradation by illegal logging and trading , the establishment of plantations ( palm oil , coconut , coffee ) , mining and forestry , and climate change . while our team are delighted with rediscovering this bat from extinction , we are still saddened by the plight of other animals such as the bramble cay melomys in nearby torres strait .

the transmitters were attached to the backs of the bats below the scapulae , usually after partially trimming the fur , and tightly glued onto the skin of the bat by using histoacrylic glue ( braun surgical , melsungen , germany ) . recaptured individuals showed no signs of any injury that could have resulted from tagging . in an attempt to visually locate feeding bats at night , some transmitters were additionally marked with a small piece of red reflecting tape .

locations of individual home ranges , and foraging and core areas . —examination of our tracking data indicates that m . macrophyllum forages exclusively over water , whereby all bats restricted their flight activity predominantly to the immediate shoreline of gatun lake ( within approximately 50 m ) . this resulted in most cases in distinctly elongated home - range shapes ( fig . 1 ) . we have no evidence that bats also used the forest as a hunting habitat . except for bat m2 , which spent most of its foraging time around colorado point ( fig . 2a ) , males in general and a harem male ( m3 ) in particular , used small foraging and core areas that were located in laboratory cove or bat cove , that is , in close proximity to their day roost in the barracuda ( fig . 2b ) . females , in contrast , were much more variable , having foraging and core areas both close to and very distant from the day roost ( figs . 2c - f ) .

the species chosen for this study inhabit the andean cloud forest ( > 2 , 000 m elevation ) and belong to each of the 3 different dietary types found in this ecological unit . thus , we worked with anoura latidens , a nectar–polinivorous species with a wide elevational range ( 50–2 , 240 m ) but found most frequently in montane localities ( handley 1984 ) ; sturnira erythromos , a frugivorous bat that occurs in montane environments with a narrow elevation range in venezuela ( 1 , 000–2 , 500 m— handley 1976 ) ; and tadarida brasiliensis , an insectivorous bat with a wide distribution range , which includes subtropical regions of north and south america and the tropical andes ( wilkins 1989 ) . in south america , t . brasiliensis seems to be absent in the amazonian basin , and although it seems to prefer the mountain region in the neotropics ( up to 2 , 107 m— handley 1976 ) , this species may be found at low elevations ( koopman 1982 ; wilkins 1989 ) .

use of foraging and core areas . —although overall ranges were large , m . macrophyllum concentrated its activity in small core - use areas of typically less than 10 ha , representing roughly 35 % of the size of foraging areas . there was moderate spatial overlap between foraging and core areas of individual bats ( fig . 2 ) . however , because we were only able to track 1 bat at a time , we could not test whether there was also temporal overlap in the use of feeding sites .

all five groups of bat - catching spider taxa ( nephilidae , araneidae , theraphosidae , sparassidae , and pisauridae ) are known to be predominantly predaceous on insects [ 14 ] , [ 53 ] , [ 64 ] , [ 69 ] , [ 101 ] . with regard to large - sized theraphosids , sparassids , and pisaurids , their feeding behavior in the field has not been thoroughly investigated and one cannot currently judge whether predation on bats is of significance to them from a feeding ecological point of view .

database . —between april and july 2002 , 10 bats ( 6 females and 4 males ) were tagged for radiotracking . data from 1 female that lost the transmitter by the beginning of the 3rd night of tracking were excluded from analyses . the database thus consisted of 5 females and 4 males ( hereafter referred to as f1–f5 and m1–m4 , respectively ) that were tracked for an average of 5 . 3 nights ± 0 . 9 sd each . this led to 519 . 5 h of tracking with on average 422 . 5 h ( 82 % ) of contact time ( range = 55–100 % ) during which a bat could be followed closely .

this insectivorous species shows the lowest basal metabolic rate and thermal conductance measured for any tropical bat ( 42 % and 68 % , respectively , of expected values for their body mass ; table 1 ) . these values appear below the 95 % confidence limit for regressions for lowland insectivorous bats , both for basal metabolic rate and for thermal conductance as a function of body mass . likewise , t . brasiliensis shows the lowest values known for upper and lower critical temperatures ( table 1 ) . although some of these features differ from those found for the nectarivores and frugivores examined in this study , they are in agreement with what can be expected for insectivorous bats .

the nectarivorous bat , a . latidens , is endothermic and has a high basal metabolic rate ; however , its high thermal conductance and lower critical temperature do not show an adaptation to cool environments as expected . further data from additional individuals are necessary to characterize this species . the frugivore s . erythromos has a high basal metabolic rate and maintains thermal conductance as expected , which implies a very important displacement of thermoneutral zone to lower temperatures . at temperatures below the lower critical temperature , some bats express a hypothermic response or facultative torpor . one insectivore , t . brasiliensis , has very low basal metabolic rate and thermal conductance and a thermoneutral zone range displaced toward lower temperatures , and all the individuals enter obligate torpor at ambient temperatures < 22°c .

fostered by recent advances in transmitter miniaturization , radiotracking has proven a particularly powerful technique for investigating many aspects of bat ecology , including home - range requirements and patterns of space and habitat use . however , so far most detailed radiotracking studies have concentrated on temperate - zone species ( e . g . , catto et al . 1996 ; entwistle et al . 1996 ; leonard and fenton 1983 ; robinson and stebbings 1997 ; wai - ping and fenton 1989 ) , whereas relatively few studies have been conducted in the tropics ( e . g . , bernard and fenton 2003 ; charles - dominique 1991 ; fenton et al . 1993 ; fleming 1988 ; gannon and willig 1997 ; kalko et al . 1999 ; morrison 1978 ; reviewed in kalko 1998 ) .

anatomical features such as very dense fur , absence of an uropatagium , small ears , and densely haired feet and toes ( de la torre 1961 ) can partially compensate for the tendency for rapid heat loss caused by high temperature differentials between the bat and the ambient air . an additional feature is the dual response that s . erythromos shows to temperatures below the lower critical temperature , which we interpret as facultative torpor . we observed that individuals could respond as typical normotherms or as hypotherms ( fig . 2 ) . as hypotherms , bats entered reversible torpor and decreased their body temperature ( hypothermia ) . this physiological response allows them to reduce energetic expenditures . s . lilium can economize between 10 % and 30 % of its reserves under similar conditions via hypothermia ( audet and thomas 1997 ) .

absolute and mass - specific values of basal metabolic rate obtained for the montane nectarivorous bat a . latidens are among the highest known for glossophagine bats ( table 1 ) . the high basal metabolic rate permits a . latidens to maintain constant body temperature . such physiological response has been demonstrated previously for mammals with feeding habits based on carbohydrates ( mcnab 1986 ) . all representatives of the genus anoura inhabit mountain environments and use caves , caverns , and rocky shelters as diurnal refuges , where they roost in small groups ( lemke and tamsitt 1979 ) . within diurnal refuges , they are exposed to ambient temperatures below their lower critical temperature ( 19°c—a . ruiz , in litt . ) ; consequently , high basal metabolic rate allows them to resist the temperature differential between their body and the environment ( arends et al . 1995 ) .

this frugivorous bat shows both the highest mass - specific basal metabolic rate among those known for lowlands and a high value among frugivore bats for minimal thermal conductance ( table 1 ) . the basal metabolic rate of s . erythromos is above the 95 % confidence limit for the regression obtained for the mass - specific basal metabolic rate of frugivore bats from neotropical lowlands . its thermal conductance value places it at the upper end of the expected range for a regression line of lowland frugivorous bats ( table 1 ) . on the other hand , the range of thermoneutral zone is the smallest of the guild ( table 1 ) , and s . erythromos also shows the lowest lower critical temperature in relation to size ; this value is shared with other much larger species such as artibeus jamaicensis and a . lituratus ( table 1 ) .

in the tropics , huge nephilid orb - webs ( genera nephila and nephilengys ) sometimes block the entrances to bat caves ( [ 61 ] ; c . dietz , pers . comm . ) . such cave entrance inhabiting nephilid populations have been discovered in east and south east asia as well as in the neotropics . so far it is unknown to what extend cave - roosting bats flying back and forth between caves and foraging areas are able to detect and avoid these webs . since it is hypothesized that the bats might navigate by spatial memory while passing through cave entrances [ 121 ] , it is conceivable that some of them may crash into nephilid webs within the cave’s entrance zone , given the fact that in some areas they leave caves at dusk in gigantic swarms . monitoring nephild webs at cave entrances by means of video recording devices could bring an answer to this question .

another factor that influences home - range size , in addition to foraging mode , is availability and distribution of food in space and time . small aerial insects , in contrast to , for instance , frogs , which often occur aggregated at spawning pools , are more widely distributed throughout the landscape . thus , bats like m . macrophyllum exploiting this resource should travel longer distances on a nightly basis and have large home ranges . for instance , weinbeer and kalko ( 2004 ) found average home ranges of 46 ha ( range 19–158 ha ) for the insectivorous bat lampronycteris brachyis ( phyllostomidae ) on barro colorado island . similar to m . macrophyllum ( weinbeer et al . , in press ) , this species was characterized by a high flight activity of more than 3 h per night , during which the bats traveled estimated distances of several dozen kilometers ( m . macrophyllum : about 35–50 km , l . brachyotis : approximately 60 km ) , paralleling many aerial insectivorous vespertilionids .

the neotropical orb - weaving spider nephila clavipes has been witnessed catching bats quite frequently ( 9 reports ) , but in none of these cases was it seen biting , wrapping or eating a bat . likewise , birds trapped in the webs of this spider species were apparently not consumed [ 22 ] – . only once has a neotropical nephila been observed biting a bird , but without subsequent consumption of the prey [ 22 ] . it has been suggested that nephila clavipes might be unable to deal with large , aggressive prey such as bats and birds [ 24 ] , [ 27 ] . if this latter assumption is true , then the captures of bats in the webs of nephila clavipes would be cases of non - predation deaths ( the bats dying of exhaustion , starvation , dehydration , and / or hyperthermia ) . the two european incidences where bats were killed in spider webs without the spiders feeding on them must be considered to have been cases of non - predation deaths as well .

in recent years , the idea has been proposed that the occasional catch of large , energetically rewarding prey may be essential in order to fulfil the reproductive needs of large orb - weaving spiders ( “rare , large prey” hypothesis ; see [ 122 ] – [ 123 ] ) . while large orb - weavers such as nephila spp . capture predominantly small insects of little energetic value , they derive the bulk of their energy from a few rare , large prey items ( see [ 46 ] , [ 49 ] , [ 53 ] , [ 122 ] ) . in this context “rare , large prey” encompasses large insects ( e . g . , cicadas , moths , coleopterans , orthopterans , and odonates ) as well as small flying vertebrates ( bats and birds ) . in our opinion , the examples of bat - eating orb - weavers reported in this paper are consistent with the " rare , large prey " hypothesis , though one may object to this given the rarity of such events .

the ancova analysis ( table 1 ) of data available for 21 tropical bat species and the 3 species in this study indicates that log 10 of basal metabolic rate is significantly correlated with log 10 of body mass ( p = 0 . 0035 , r 2 = 0 . 40 ) and with food habits ( p = 0 . 00002 ) . it is not significantly correlated with maximal elevation range ( p = 0 . 56 ) . although elevation did not show an effect on log 10 of basal metabolic rate , when both elevation and food habits are taken into account , a statistically significant impact on log 10 of metabolic rate was obtained ( p = 0 . 0002 ) . this implies that elevation does not have the same effect as diet on metabolic responses of the various dietary groups examined . our results seem to show that both the nectarivorous a . latidens and the frugivorous s . erythromos increase their basal metabolic rate as a response to elevation , whereas the insectivorous t . brasiliensis shows the opposite response , probably as a consequence of its poor energetic budget .

the lowest temperature at which a bat maintained its basal metabolic rate ( lower critical temperature ) was determined by finding the intersection between regression lines with best fit to data , calculated by minimal squares method for values inside and below the zone of thermal neutrality ( nickerson et al . 1989 ) . in the case of a . latidens , the method of nickerson et al . ( 1989 ) was not feasible because this species showed different conductances in and below thermal neutrality ; consequently , we define lower critical temperature as the minimal value of ambient temperature in which the range of basal metabolic rate was independent of ambient temperature . an approximation to upper critical temperature was obtained as the inflection point in metabolic rate as ambient temperature increased . differences in metabolic rate as well as in thermal conductance between normothermic and hypothermic bats were tested using 1 - way analysis of variance . analysis of covariance ( ancova ) was used to test the impact of various factors on basal rate of different species of tropical bats for which data were available from the literature . thus , log 10 of basal metabolic rate = f ( log 10 body mass , maximal elevation range , and diet ) .

movement patterns . —commuting distances between day roost and nearest foraging area ranged from 0 to 4 . 35 km , with no significant difference between the sexes ( males : median = 0 km , iqr = 0 km ; females : 0 . 040 km , iqr = 0–3 . 38 km ; z = –1 . 60 , p = 0 . 109 ) . except for 2 females ( fl and f4 ) whose single foraging areas were located more than 2 and 4 km away from the day roost , the majority of individuals had their closest foraging area directly adjacent to their day roost . in commuting between day roost and feeding areas or between the latter , tagged individuals typically did not fly the most direct route , which would have led them through forest , but closely followed the shoreline or flew over open water instead . some bats ( m1 , m2 , and f1 ) flew over or crossed only small , forested areas en route to their foraging areas . during commutes along the shoreline , the bats attained a flight speed of approximately 8 . 3 m / s ( 30 km / h ) as estimated based on the speed of our motorboats ( determined by use of a global positioning system unit ) while closely tracking a bat .


stalk-eyed flies are insects of the fly family diopsidae .

the family is distinguished from most other flies by the possession of " eyestalks " : projections from the sides of the head with the eyes at the end .

some fly species from other families such as drosophilidae , platystomatidae , richardiidae , and tephritidae have similar heads , but the unique character of the diopsidae is that their antennae are located on the stalk , rather than in the middle of the head as in all other flies .

the stalk-eyed flies are up to a centimeter long , and they feed on both decaying plants and animals .

their unique morphology has inspired research into how the attribute may have arisen through forces of sexual selection and natural selection .

studies of the behavior of the diopsidae have yielded important insights into the development of sexual ornamentation , the genetic factors that maintain such a morphological feature , sexual selection , and the handicap principle .

stalk - eyed fly

stalk - eyed fly <EOT> stalk eyed fly pc : rob knell ( cc by sa 2 . 5 )

signalling fitness : larger males sire more offspring . studies of the stalk - eyed fly

. signalling fitness : larger males sire more offspring . studies of the stalk - eyed fly

female choice response to artificial selection on an exaggerated male trait in a stalk - eyed fly .

female preference response to artificial selection on an exaggerated male trait in a stalk - eyed fly .

mating - induced reduction in accessory reproductive organ size in the stalk - eyed fly cyrtodiopsis dalmanni .

. female preference response to artificial selection on an exaggerated male trait in a stalk - eyed fly .

hingle a , fowler k , pomiankowski a . size - dependent mate preference in the stalk - eyed fly

lorch pd , wilkinson gs , reillo pr . copulation duration and sperm precedence in the stalk - eyed fly

burkhardt d , de la motte i . how stalk - eyed flies eye stalk - eyed flies : observations and measurements of the eyes of

burkhardt d . and motte i , 1983 . how stalk - eyed flies eye stalk - eyed flies : observations and measurements of the eyes of

university college london , department of biology ; 2003 . the evolution of multiple mating in the stalk - eyed fly ,

mating - induced reduction in accessory reproductive organ size in the stalk - eyed fly cyrtodiopsis dalmanni . - pubmed - ncbi

condition dependence of sexual ornament size and variation in the stalk - eyed fly cyrtodiopsis dalmanni ( diptera : diopsidae ) .

whether sexually selected traits are sex linked can have profound effects on their evolution . in the diopsid stalk - eyed fly ,

cotton s , fowler k , pomiankowski a . condition dependence of sexual ornament size and variation in the stalk - eyed fly

male sexual ornament size but not asymmetry reflects condition in stalk - eyed flies .

evolution of genetic variation for condition - dependent traits in stalk - eyed flies .

. coevolution of sperm and female reproductive tract morphology in stalk - eyed flies .

. evolution of genetic variation for condition dependent traits in stalk - eyed flies .

visual system of the stalk - eyed fly , cyrtodiopsis quinqueguttata ( diopsidae , diptera ) : an anatomical investigation of unusual eyes .

wilkinson gs , reillo pr . female preference response to artificial selection on an exaggerated male trait in a stalk - eyed fly .

hingle a , fowler k , pomiankowski a . the effect of transient food stress on female mate preference in the stalk - eyed fly

. male sexual ornament size but not asymmetry reflects condition in stalk - eyed flies .

wilkinson g . s . , 1993 . artificial selection alters allometry in the stalk - eyed fly cyrtodiopsis dalmanni ( diptera : diopsidae ) .

condition dependence of sexual ornament size and variation in the stalk - eyed fly cyrtodiopsis dalmanni ( diptera : diopsidae ) . - pubmed - ncbi

selective pressures , variability , and sexual dimorphism in stalk - eyed flies ( diopsidae ) .

. male eye span in stalk - eyed flies indicates genetic quality by meiotic drive suppression .

rogers dw , chapman t , fowler k , pomiankowski a . mating - induced reduction in accessory reproductive organ size in the stalk - eyed fly

. hunting for ayv 28—right and wrong approaches in an attempt to increase our knowledge about the stalk - eyed fly ( diopsidae , diptera ) .

visual system of the stalk - eyed fly , cyrtodiopsis quinqueguttata ( diopsidae , diptera ) : an anatomical investigation of unusual eyes . - pubmed - ncbi

panhuis tm , wilkinson gs . exaggerated eyespan influences male contest outcome in stalk - eyed flies .

wilkinson gs , fry cl . meiotic drive alters sperm competitive ability in stalk - eyed flies .

hurley i , pomiankowski a , fowler k , smith h . , 2002 . fate map of the eye antennal imaginal disc in the stalk - eyed fly

so , the benefit that the compound eye gives the fly is that the fly can see . it lets the fly know if something is coming towards it , where the fly is positioned in its environment , what’s there , and tells the fly that it’s moving in relation to other things .

rogers dw , grant ca , chapman t , pomiankowski a , fowler k . the influence of male and female eyespan on fertility in the stalk - eyed fly

stalk - eyed flies ( diopsidae ) : modelling the evolution and development of an exaggerated sexual trait .

presgraves dc , severance e , wilkinson gs . sex chromosome meiotic drive in stalk - eyed flies .

figure 16 : a species of stalk - eyed flies photographed in dairy farm . courtesy of nicky bay .

wilkinson gs , kahler h , baker rh . evolution of female mating preferences in stalk - eyed flies .

is the only stalk - eyed fly in the micropezidae family – and we only have one , slightly damaged specimen in the collection . on the right : the essay unwrapped .

wilkinson gs . genetic consequences of sexual selection in stalk - eyed flies . in : dugatkin la , editor .

cotton s , rogers dw , small j , pomiankowski a , fowler k . variation in preference for a male ornament is positively associated with female eyespan in the stalk - eyed fly

the full importance of the accessory glands in stalk - eyed fly reproduction is poorly understood . accessory gland products form the casing of the spermatophore and consequently are necessary for sperm transfer [

fry cl . juvenile hormone mediates a trade - off between primary and secondary sexual traits in stalk - eyed flies .

baker rh , denniff m , futerman p , fowler k , pomiankowski a , chapman t . accessory glands influence time to sexual maturity and mating frequency in the stalk - eyed fly ,

rogers dw , baker rh , chapman t , denniff m , pomiankowski a , fowler k . direct and correlated responses to artificial selection on male mating frequency in the stalk - eyed fly

lorch p . , wilkinson g . s . , reilo pr . , 1993 . copulation duration and sperm precedence in malaysian stalk - eyed fly , cyrtodiopsis whitei ( diptera : diopsidae ) .

baker rh , ashwell ris , richards ta , fowler k , chapman t , pomiankowski a . effects of multiple mating and male eye span on female reproductive output in the stalk - eyed fly

stalk - eyed flies ( diopsidae ) : modelling the evolution and development of an exaggerated sexual trait . - pubmed - ncbi

reguera p . , and pomiankowski , a . , 2004 . low cost of reproduction in female stalk - eyed flies ,

reguera p , pomiankowski a , fowler k , chapman t . low cost of reproduction in female stalk - eyed flies ,

wilkinson gs , reillo pr : female choice response to artificial selection on an exaggerated male trait in a stalk - eyed fly . proc r soc lond b . 1994 , 255 : 1 - 6 .

burkhardt d , de la motte i . selective pressures , variability , and sexual dimorphism in stalk - eyed flies ( diopsidae )

wilkinson gs et al . , " sex - biased gene expression during head development in a sexually dimorphic stalk - eyed fly . " , plos one , 2013 mar 19 ; 8 ( 3 ) : e59826

big ‘antlers’ are favoured : female choice in stalk - eyed flies ( diptera , insecta ) , field collected harems and laboratory experiments .

david p , bjorksten t , fowler k , pomiankowski a . condition - dependent signalling of genetic variation in stalk - eyed flies .

sukontason kl , chaiwong t , piangjai s , upakut s , moophayak k , et al . ( 2008 ) ommatidia of blow fly , house fly , and flesh fly : implication of their vision efficiency . parasitol res 103 : 123–131 .

kotrba m . , 2004 . baltic amber fossils reveal early evolution of sexual dimorphism in stalk - eyed flies ( diptera : diopsidae ) .

the australian museum has the world ' s largest and most comprehensive collection of signal flies , including examples from 64 different species of stalk - eyed signal fly and a number of unique specimens found in no other museum collection .

sukontason kl , chaiwong t , piangjai s , upakut s , moophayak k , and sukontason k . 2008 . ommatidia of blow fly , house fly , and flesh fly : implication of their vision efficiency . parasitology research 103 : 123 - 131 .

burkhardt d . , and motte i . , 1985 . selective pressure , variability and sexual dimorphism in stalk - eyed flies ( diopsidae ) .

stalk - eyed signal flies occur mainly in new guinea ( with more than 90 recorded species ) and in queensland ( with five recorded species ) .

. big ` antlers ' are favoured : female choice in stalk - eyed flies ( diptera , insecta ) , field collected harems and laboratory experiments .

male stalk - eyed signal flies spend much of their time in rainforests on shaded tree trunks which they use as courtship territory and avidly defend against rivals .

the heritability of sexually dimorphic traits in the yellow dung fly scatophaga stercoraria ( l . )

a male big eyed fly . its entire head is a pair of eyes . ( diptera : pipunculidae ) pc : marcello consolo ( cc by sa 2 . 0 )

panhuis t . m . , wilkinson g . s . , 1999 . exaggerated male eye span influences contest outcome in stalk - eyed flies ( diopsidae ) .

wright tf , johns pm , walters jr , lerner ap , swallow jg , wilkinson gs . microsatellite variation among divergent populations of stalk - eyed flies , genus

^ wilkinson g . s . , and reillo p . r . , 1994 . female choice response to artificial selection on an exaggerated male trait in a stalk - eyed fly . proceedings of biological sciences . 255 ( 342 ) : 1 - 6 .

sometimes evolution just doesn’t care if you can see and it’s only important how sexy you are . that’s what happened to the stalk eyed fly . the outrageous stalks that the males carry around actual hinder their flying capabilities but they can still see relatively well .

a soldier fly . the red color acts as a pair of sunglasses . pc : eddie smith

studies on the egg morphology of stalk - eyed flies using scanning electron microscope ( sem ) demonstrated that egg morphology is useful for identification purposes and for cladistic analysis .

baker rh , wilkinson gs , desalle r . the phylogenetic utility of different types of molecular data used to infer evolutionary relationships among stalk - eyed flies ( diopsidae )

^ rihak g . , egge a . r . , swallow g . s . , 2009 . saccadic head rotations during walking in the stalk - eyed fly ( cyrtodiopsis dalmanni ) . proceedings of the royal society of biological sciences . 276 : 1643 - 1649 .

this video shows three stalk - eyed fly species from borneo ( teleopsis pallifacies , eurydopsis sarawakensis , cyrtodiopsis sp . ) and features information on their mating biology . it also shows a surprise attack ! ! follow me on twitter @ magsorger # crazybeautifulnature visit my website urltoken

figure 3 : eyes of a stalk - eyed flies , showing the position of antenna beside the compund eye . [ image courtesy of tronghieusg , used with permission . ]

. this suggest that the behavior of aggregating and intrasexual competition between males , besides sexual selection , is a selection force for sexual dimorphsim in the stalk - eyed flies .

fry cl , wilkinson gs : sperm survival in female stalk - eyed flies depends on seminal fluid and meiotic drive . evolution . 2004 , 58 : 1622 - 1626 .

baker rh et al . , " genomic analysis of a sexually - selected character : est sequencing and microarray analysis of eye - antennal imaginal discs in the stalk - eyed fly teleopsis dalmanni ( diopsidae ) . " , bmc genomics , 2009 aug 5 ; 10 : 361

male and female of a blow fly . ( chrysomya rufifacies ) pc : sukontason et al . 2008

life returns to discovery channel in october - sundays starting 10 / 3 @ 8 and 9p ! urltoken stalk - eyed flies inflate their long , tube - like eye stalks .

the most notable example where this occurs is the family of flies called diopsidae . every species has eye stalks and so they are the ones commonly called the stalk - eyed flies .

it should be noted that stalk - eyed flies are not the only group of dipteran flies that posses eye stalks ( figure 2 ; click here for examples of dipteran with eye stalk ) . however , they are unique by having the antenna near the end of the eyes stalk , next to the eye instead of in the facial region ( figure 3 ) .

burkhardt d , de la motte i . big ' antlers ' are favoured : female choice in stalk - eyed flies ( diptera , insecta ) , field collected harems and laboratory experiments .

stalk - eyed flies ( family diopsidae ) are a model system for studying sexual selection due to the elongated and sexually dimorphic eye - stalks found in many species . more . . .

^ wilkinson g . s . , johns p . m . , kelleher e . s . , muscedere m . l . , lorsong a . , 2006 . fitness effects of x chromosome drive in the stalk - eyed fly , cyrtodiopsis dalmanni . journal of evolutionary biology . 19 : 1851–1860 .

is definitely the lateral head projection ( the “eye stalk” ) , which bore the eyes and the antenna . the eye stalk is derived from the posterior half of the eye - antennal disc

we have shown that the pattern of sperm usage is highly variable in the stalk - eyed fly , t . dalmanni . this greatly limits the utility of population - based estimates of p 2 as descriptors of sperm usage , and suggests that sperm precedence should be viewed as context - specific , rather than a general , constant , metric in stalk - eyed flies . the unexplained variance in male fertilization success found by this study requires further investigation in order to evaluate potential causes and consequences .

^ cotton s . , small j . , hashim r . , pomiankowski a . , 2010 . eyespan reflects reproductive quality in wild stalk - eyed flies . evolutionary ecology . 24 : 83–95 .

husak j . f . , ribak g . , wilkinson g . s . , swallow j . g . , 2011 . compensation for exaggerated eye stalks in stalk - eyed flies ( diopsidae ) .

1 . outer vertical bristle black twice as long as width of eye - stalk in the middle .

most times this just involves squaring up to each other like alcohol - infused humans . but sometimes the fights become more physical , with males head butting each other or having fist fights . yes , proper fly - on - fly boxing .

^ rogers d . w . , baker r . h . , chapman t . , denniff m . , pomiankowski a . , fowler k . , 2005 . direct and correlated responses to artificial selection on male mating frequency in the stalk - eyed fly cyrtodiopsis dalmanni . journal of evolutionary biology . 18 : 642 - 650 .

stalk - eyed flies of the family diopsidae exhibit a unique form of hypercephaly , which has evolved under both natural and sexual selection . male hypercephaly is used by female diopsids as an indicator of male quality . by choosing to mate with males expressing the most - exaggerated hypercephaly , females can benefit both from the enhanced fertility of these males and the transmission of other heritable advantages to their offspring . stalk - eyed flies are close relatives of the model organism , drosophila melanogaster . we have shown that similar genetic and cellular mechanisms regulate the initial development of the head capsule in fruitflies and diopsids . the great diversity of stalk - eyed fly species , exhibiting varying degrees of hypercephaly and sexual dimorphism , constitutes a major advantage for comparative studies of their development and evolution .

my first experience of stalk - eyed flies came while i was carrying out fieldwork in costa rica over 10 years ago and it can probably go down as one of my favourite fieldwork moments . so what happened ?

it is not just the richardiidae family that contain stalk - eyed species , in fact the stalk - eyed condition has evolved independently in at least eight families of flies . in these families , and generally only in males , the eyes have migrated away from the head and are now found on the end of stalks . called hypercephalization , this condition also includes examples where elaborate structures such as antlers and horns protrude from the head .

richard h . baker , robert i . s . ashwell , thomas a . richards , kevin fowler , tracey chapman , andrew pomiankowski ; effects of multiple mating and male eye span on female reproductive output in the stalk - eyed fly , cyrtodiopsis dalmanni , behavioral ecology , volume 12 , issue 6 , 1 november 2001 , pages 732–739 , urltoken

diopsinae is a taxonomic group of fly in which members posse the eye stalks . this group is nested within the diopsidae , the stalk - eyed flies . however , taxonomists do not agree with what constitute the diopsidae . the traditional definition of diopsidae includes the centrioncinae , in which members do not have the eye stalks , and the diopsinae . however , some taxonomists argue that the centrioncinae should not be included in the diopsidae , and should treat as a different group . [ 20 ] stalk - eyed flies in this page refers to the members of diopsidae that includes centrioncinae .

this group of flies contains some spectacular species including the stalk - eyed signal flies , belonging to the genus achias . true to their name , the males have eyes on long stalks extending from either side of their heads .

the signal fly family ( platystomatidae ) includes a great diversity of species found in australia , new guinea and other nearby tropical countries .

scientists working on this family estimate that there may be as many as 900 species of signal fly that occur in the australasian region .

kirschfeld k , franceschini n , minke b ( 1977 ) evidence for a sensitising pigment in fly photoreceptors . nature 269 : 386–390 .

the common horse fly may seem an ugly nuisance from far away , but in the macro perspective , its eyes draw you in .

the band - eyed drone fly is a bee mimic , and it takes the ruse to the limit , with stripes even on its eyes . but why ? scientists hypothesize that it affects what this insect sees — definitely a subject for further research .

land mf , eckert h ( 1985 ) maps of the acute zones of fly eyes . journal of comparative physiology a 156 : 525–538 .

this deer fly has a distinct pattern on its eyes . in fact , their genus , chrysops , translates to " gold eyes . "

most of the described stalk - eyed flies species are found in the old world with the afrotropical region having the most species . there is only two species found in the new world and are found in temperate north america . the distribution of

this entry was posted in ecology , physiology and tagged compound eye , diptera , eyes , fly , insect , ommatidia . bookmark the permalink .

ribak g and swallow jg . 2007 . free flight maneuvers of stalk - eyed flies” do eye - stalks effect aerial turning behavior ? journal of comparative physiology a neuroethology , sensory , nuerual , and behavioral physiology 193 ( 10 ) : 1065 - 1079 .

till date , there is no proper studies in surveying the diversity of stalk - eyed flies in singapore , but they have been photographed by photography enthusiasts in matritchie reservoir park , dairy farm ( figure 16 ) , singapore botanic garden , bukit timah and nee soon swamp forest ( map ) . teleopsis dalmanni could be found in central catchement area . stalk - eyed flies are generally found at shady areas , near edge of forest streams , or in wet muddy area with rotten vegetation in proximate ( figure 17 ) .

imagine seeing through the extended eyes of the stalk - eyed fly ! these funky - looking bugs can extend their eyes outward by filling their heads with air as they make their final transformation from pupa to adult ( see this amazing process in this discovery " life " video ) . while it seems as though these outward - facing eyes might provide superior vision , the main purpose is to attract female flies .

cotton , a j földvári , m cotton , s and pomiankowski , a 2014 . male eyespan size is associated with meiotic drive in wild stalk - eyed flies ( teleopsis dalmanni ) . heredity , vol . 112 , issue . 4 , p . 363 .

wernet mf , desplan c ( 2004 ) building a retinal mosaic : cell - fate decision in the fly eye . trends in cell biology 14 : 576–584 .

update ( 22 jan . 13 ) : thanks to hans feijen for identifying the fly species , which turned out to be diasemopsis fasciata , and not diopsis .

fly , ( order diptera ) , any of a large number of insects characterized by the use of only one pair of wings for flight and the reduction of the second pair of wings to knobs ( called halteres ) used for balance . the term fly is commonly used for almost any small flying insect . however , in entomology…

bath , eleanor wigby , stuart vincent , claire tobias , joseph a . and seddon , nathalie 2015 . condition , not eyespan , predicts contest outcome in female stalk - eyed flies , teleopsis dalmanni . ecology and evolution , vol . 5 , issue . 9 , p . 1826 .

bonduriansky r , rowe l ( 2003 ) interactions among mechanisms of sexual selection on male body size and head shape in a sexually dimorphic fly . evolution 57 : 2046–2053 .

within the fruit fly family , tephritidae , there are two species that have stalked eyes . one of them , pelmatops ichneumonea , was once placed in a different genus and family . in fact , it is easy to see at first glance why this happened when you compare it with achias , the genus it was originally described as . achias is now within the platystomatidae family and contains arguably the most impressive of all of the stalk - eyed flies – achias rothschildii .

^ wilkinson , g . s . , amitin , e . g . and johns , p . m . , 2005 . sex - linked correlated responses in female reproductive traits to selection on male eye span in stalk - eyed flies . integrative and comparative biology . 45 : 500 - 510 .

shortly after eclosion , before their structures hardened , t . dalmanni ingest air thorough their oral cavity , and pump it to the tips to their stalk through a duct in the head , thereby elongating their stalk . watch the video to see an newly - emerged adult flies pumping their eye stalks !

3 . inner vertical bristle up to 4 . 5–5 times as long as width of eye - stalk in the middle ; on a small tubercle .

^ ribak g . , pitts m . l . , wilkinson g . s . , swallow g . s . , 2009 . wing shape , wing size , and sexual dimorphism in eye - span in stalk - eyed flies ( diopsidae ) . biological journal of the linnean society . 98 : 860–871 .

stalk - eye flies shared the same general life history pattern ( figure 18 ) , although fecundity , age of sexual maturity and longevity varies among species .

^ worthington a . m . , berns c . m . , and swallow j . g . , 2012 . size matters , but so does shape : quantifying complex shape changes in a sexually selected trait in stalk - eyed flies ( diptera : diopsidae ) . biological journal of the linnean society . 106 : 104–113 .

hardie rc ( 1985 ) functional organization of the fly retina . progress in sens physiol . berlin , heidelberg , new york , toronto : springer , vol . 5 . pp . 1–79 .

before the museum exhibition about colour and vision closes on 6 november , i thought i should write a piece about some of nature’s most amazing eyes ( their patterns and shapes ) . i’m talking of course about those belonging to flies – the most enigmatic of all species on the planet – and specifically all the species referred to as stalk - eyed flies .

within micropezidae there is only one species that exhibits the stalk - eyed condition : anaeropsis guttipennis . and within our collection there is only one , slightly damaged specimen that only has one stalk ! however beside this specimen is an essay – albeit the smallest of essays . unwrapped , this essay ( by ernest edward austin – a great dipterist and my forefather in curation terms ) describes how several authors have moved the taxonomic placement of this species around . ernest felt that any decisions to be made needed further proof and greater comparisons – wise words .

fascinating , erica ! do such structures occur in just flies ? is it possible that they fulfill functions other than visual superiority of some kind and sexual prowess ? i note the forward rake in some species , which half suggests equivalence to antennae in lepidoptera… that visual superiority , if it exists… i wonder if having the eyes on stalks enables fuller all - round vision – because the optically - facetted part of the stalk - side of each eye fills - in the blind spot in normal flies caused by the head . that might be an evolutionary driver for just thin - stalked eyes . but then why the species with thick - stalked eyed ? one also wonders if the stalked - eyes structure helps with orientation awareness , it’s inertia tending to keep it at a fixed orientation , in turn enabling the fly to sense changes in the orientation of its body . …related to the gyroscopic function of halteres . but then , non - stalk - eyed flies seem to manage well enough without… …so many questions… mike

the base stock was an outbred laboratory population of the stalk - eyed fly , c . dalmanni , collected from gombak , malaysia in 1993 . the stock was maintained in large cages at high population size ( typically more than 200 individuals per cage ) and with a 1 : 1 sex ratio . flies were fed ground corn medium and kept at 25°c on a 12 h / 12 h light / dark regime . the regime included a 15 - min " dawn " period in which the culture room was illuminated by a single 60 - w bulb . all observations of behaviour commenced at the start of this dawn period .

that is , of course , if the organism needs to see . eyes are usually the first things to disappear if you live in caves . or if you’re a fly maggot that invests its early days face first eating rotting corpses .

the distribution of second male sperm precedence ( p 2 ) among 22 dam - sire pair families in the stalk - eyed fly , teleopsis dalmanni . open bars depict the frequency of families with p 2 significantly different from 0 . 5 ( using 2 - tailed binomial tests ) ; black bars denote those with p 2 not significantly different from 0 . 5 . the grey bar denotes the sperm precedence of a single family where the observed p 2 of zero was not significantly different from p 2 = 0 . 5 . however , the brood size of this family was small ( n = 5 ) , so this result should be treated with caution .

internal reproductive organ size is an important determinant of male reproductive success . while the response of testis length to variation in the intensity of sperm competition is well documented across many taxa , few studies address the importance of testis size in determining other components of male reproductive success ( such as mating frequency ) or the significance of size variation in accessory reproductive organs . accessory gland length , but not testis length , is both phenotypically and genetically correlated with male mating frequency in the stalk - eyed fly cyrtodiopsis dalmanni . here we directly manipulate male mating status to investigate the effect of copulation on the size of both the testes and the accessory glands of c . dalmanni .

since males with longer eye span gain benefits of having more mating opportunities , there is a strong sexual selection force for increasing longer eye stalks in males . however , there is a limit in the length of the eye stalks . the process of developing longer eye stalk could create developmental problems in the larvae stage , leading to high larvae mortality rate in the pupae stage . longer eye stalk also requires longer development time , which increase the exposure to toxic metabolites produced by conspecific larva , as well as to predators and parasites . therefore , the length of male eye stalk is maintain by natural selection opposing the force of sexual selection .

we thank t . chapman and g . hurst for comments , and a . hingle for help in rearing fly stocks . this work was supported by royal society university research fellowships ( k . f . and a . p . ) and the nerc .

there are about 150 , 000 described species of described true flies ( diptera ) with an estimated total number of fly species to be around 240 , 000 . so , this is going to be very generalized and does not at all encompass every organism .

male mating history is often associated with changes in male investment in current mating attempts , with concomitant effects on patterns of paternity [ 12 , 13 ] . however , all males were virgins at the start of the experiment and performed equal numbers of copulations , so variation in mating experience did not differ between first and second males , and hence is not an explanation of our data . in addition , all males were maintained on a high quality diet , so variation in environmental conditions was minimised between pairs of sires . these factors ( when variable ) may well be important in determining stalk - eyed fly paternity and deserve further investigation , but they cannot explain the results reported in the current study .

in some species , females choose mates possessing ornaments that predict offspring survival 1 , 2 , 3 , 4 , 5 . however , sexual selection by female preference for male genetic quality 6 , 7 , 8 remains controversial because conventional genetic mechanisms maintain insufficient variation in male quality to account for costly preference and ornament evolution 9 , 10 . here we show that females prefer ornaments that indicate genetic quality generated by transmission conflict between the sex chromosomes . by comparing sex - ratio distributions in stalk - eyed fly ( cyrtodiopsis ) progeny we found that female - biased sex ratios occur in species exhibiting eye - stalk sexual dimorphism 11 , 12 and female preferences for long eye span 13 , 14 . female - biased sex ratios result from meiotic drive 15 , the preferential transmission of a ‘selfish’ x - chromosome . artificial selection for 22 generations on male eye - stalk length in sexually dimorphic c . dalmanni produced longer eye - stalks and male - biased progeny sex ratios in replicate lines . because male - biased progeny sex ratios occur when a drive - resistant y chromosome pairs with a driving x chromosome 15 , long eye span is genetically linked to meiotic drive suppression . male eye span therefore signals genetic quality by influencing the reproductive value of offspring 16 .

when females mate with different males , competition for fertilizations occurs after insemination . such sperm competition is usually summarized at the level of the population or species by the parameter , p 2 , defined as the proportion of offspring sired by the second male in double mating trials . however , considerable variation in p 2 may occur within populations , and such variation limits the utility of population - wide or species p 2 estimates as descriptors of sperm usage . to fully understand the causes and consequences of sperm competition requires estimates of not only mean p 2 , but also intra - specific variation in p 2 . here we investigate within - population quantitative variation in p 2 using a controlled mating experiment and microsatellite profiling of progeny in the multiply mating stalk - eyed fly , teleopsis dalmanni .

colored eyes , like those of the soldier fly above , serve a specific purpose in insects : they narrow down the information being processed by each of the tiny lenses . some insects with metallic - colored eyes have layers and layers of lenses that reflect light , lending an iridescent quality .

the length of eye stalk strongly affects the outcome of the males’ competition over a female aggregation . males with larger eyespan , independent of body size , are more aggressive and win proportionately more aggressive interaction than males with smaller eye span [ 6 ]

micropezidae , diopsidae , ottidae , platystomatidae , tephritidae , richardiidae , periscelididae and drosophilidae all contain some species that exhibit some level of hypercephalization and , interestingly , the stalk - eyed condition has evolved independently more than once in platystomatidae . this is a very good example of convergent evolution – where species that are not related have a very similar form ( the hedgehog and the spiny anteater are another good example ) . it is also an example of recurrent evolution – where a similar feature evolves time and time again .

we used the stalk - eyed fly cyrtodiopsis dalmanni to examine predictions made by condition - dependent handicap models of sexual selection . condition was experimentally varied by manipulation of larval food availability . cyrtodiopsis dalmanni is a highly dimorphic species exhibiting strong sexual selection , and the male sexual ornament ( exaggerated eyespan ) showed strong condition - dependent expression relative to the homologous trait in females and nonsexual traits . male eyespan also showed a great increase in standardized variance under stress , unlike nonsexual traits . the inflated variance of the male ornament was primarily attributable to condition - dependent ( but body - size - independent ) increase in variance . thus , evaluation of male eyespan allows females to gain additional information about male condition over and above that given by body size . these findings accord well with condition - dependent handicap models of sexual selection .

under the handicap hypothesis of mate choice , female judge the quality of males through sexual ornamentation , such as the eye stalk , which are costly to develop . a high - quality male will be able to support longer eye stalks which are costly despite poor condition

males come head to head and primarily compare stalk length . if there is a difference the male with the smaller stalks leaves and the larger male retains control of his territory ( and often harem ) . however , when they judge themselves as equal they fight !

figure 1 : mapping of compound eyes ( red ) , antenna ( green ) and eye - antenna dics ( blue ) in the stalk - eyed flies ( diopsidae ) , showing a gradual evolution of eye - stalks from condition ' a ' through ' b ' and ' c ' to ' d ' : ( a ) centrioncus prodiopsis speiser ; ( b ) sphyracephala beccari ; ( c ) sphyracephala ( pseudodiopsis ) detrahens walker ; ( d ) diopsis thoracica westwood . ( extracted and modified from meier & baker , 2002 )

stalk - eyed flies ( diptera : diopsidae ) are increasingly important model organisms for studies of sexual selection [ 19 - 22 ] . they are characterised by the lateral extension of the eyes on elongate protuberances on the side of the head capsule , a trait common to both sexes in all species [ 19 , 23 ] . in many species the eyespan of males is greater than that of females , the result of sexual selection through female mate choice [ 24 - 29 ] and male - male competition [ 30 , 31 ] .

the authors thank matthew denniff for assistance with fly rearing and behavioural observations , and two anonymous referees for their helpful comments on the manuscript . this research was funded by awards from the natural environment research council ( tc , kf & ap ) , the royal society ( tc ) and the association of commonwealth universities ( dwr ) .

both male and female stalk - eyed flies mate frequently . in the current study , each male mated an average of 3 . 79 times ( up to a maximum of 12 ) during the 60 - minute observation period . only 23 . 9 % ( 37 out of 155 ) of males mated at least 6 times and therefore 76 . 1 % ( 118 out of 155 ) of males failed to mate with all 6 virgin females provided . as females housed with three males will mate an average of 5 . 51 times during the 60 minutes following artificial dawn [

flies that rely heavily on their vision , for the most part , have cashed in on all of the options . house flies ( musca domestica ) have a moderate amount of ommatidia , but males have more ommatidia ( ~ 3 , 500 ) than females ( ~ 3 , 400 ) and bigger eyes , suggesting that vision plays an important role in mate determination . in fact , this pattern is readily seen in two other families of flies , the flesh flies ( sarcophagidae ) and the blow flies ( calliophoridae ) . house flies were at the lower end of the spectrum with some blow files coming in closer to the ~ 5 , 500 ommatidia honey bees have . while this isn’t the 30 , 000 that dragonflies have , each ommatidium of a house fly , flesh fly , or blow fly is bigger than that of a dragonfly . plus they still have a lot more than the 2 , 000 american cockroaches have and the 800 that drosophila have . so we’ll call it a nice middle ground .

when fighting face to face , rival males gauge their opponents ' size and strength from their head width . small males ( which may have begun life as under - nourished or disadvantaged larvae ) have very short or no eye - stalks . the clear difference in head - width allows the weaker fly to back off early and avoid possible injury .

many little gnats and mosquitoes are crepuscular meaning they fly at dawn and at dusk but flies generally have eye modifications for frolicking around in the sunlight . normally they’d be out of luck seeing once the sun dipped below the horizon , but flies have that 7 way split rhabdom . this helps them fly in low light conditions because the 7 parts of the rhabdom are separated and act in a similiar manner to the rhabdoms separated from the ommatidia by the clear zone . specifically for gnats and mosquitoes , it gives them an extra 15 or so minutes before dawn and after sunset . this doesn’t seem like much for us , but it gives them a small window to swarm , mate , and feed without being incredibly visible to predators .

i was walking along a path in the forest near the tropical field station la suerte ( where i was based for a month or so ) when i saw this strange creature – a hammerhead fly – scuttling over the bark of a tree . i chased it round and round the tree and finally managed to catch it in my hands ! it turned out to be this little beast –

handicap models of sexual selection predict that male sexual ornaments have strong condition - dependent expression and this allows females to evaluate male genetic quality 1 , 2 , 3 , 4 , 5 . a number of previous experiments have demonstrated heightened condition - dependence of sexual ornaments in response to environmental stress 6 , 7 , 8 , 9 . here we show that genetic variation underlies the response to environmental stress ( variable food quality ) of a sexual ornament ( male eye span ) in the stalk - eyed fly cyrtodiopsis dalmanni . some male genotypes develop large eye span under all conditions , whereas other genotypes progressively reduce eye span as conditions deteriorate . several non - sexual traits ( female eye span , male and female wing length ) also show genetic variation in condition - dependent expression , but their genetic response is entirely explained by scaling with body size . in contrast , the male sexual ornament still reveals genetic variation in the response to environmental stress after accounting for differences in body size . these results strongly support the hypothesis that female mate choice yields genetic benefits for offspring .

females of the stalk - eyed fly , cyrtodiopsis dalmanni , mate repeatedly during their lifetime and exhibit mating preference for males with large eye span . how these mating decisions affect female fitness is not fully understood . in this study , we examined the effects of multiple mating and male eye span on short - term reproductive output in this species . experiments that manipulated the number of copulations and partners a female received suggested that obtaining a sufficient sperm supply is an important benefit associated with multiple mating . the average percentage of fertile eggs laid by females increased as a function of mating frequency and ranged from 40 % for females mated once , to 80 % for females mated continuously . in addition , a high proportion of copulations in this species appeared to be unsuccessful . one - third of all females mated once laid less than 10 % fertile eggs . there was no significant difference in reproductive performance between females mated to multiple partners and females mated to a single partner . there was also no indication that females received any short - term reproductive benefits from mating with males with large eye span . in fact , females mated to males with short eye span laid a higher percentage of fertile eggs than females mated to large eye span males .

the malaysian stalk - eyed fly , teleopsis dalmanni ( formerly known as cyrtodiopsis dalmanni ; [ 32 ] ) , exhibits extreme sexual dimorphism for eyespan resulting from strong intra - and inter - sexual selection on the trait in males ( ibid . ) . females form large harems on root hairs overhanging the eroded banks of streams and males compete to control these harems [ 19 , 33 ] . both sexes are highly promiscuous and mate at high frequencies ( ~ 10 and 6 times per hour in the laboratory , for males and females respectively ; [ 34 , 35 ] ) . there is also some evidence that males strategically allocate more ejaculate to larger , more productive females through the production and delivery of larger spermatophores [ 36 ] . however , t . dalmanni spermatophores are small [ 37 ] and females store few sperm following a single mating ( ~ 140 ; [ 36 ] ) . females are therefore sperm - limited and must copulate repeatedly to attain maximal fertility [ 38 ] . this problem is exacerbated in large , highly fecund females despite being allocated more ejaculate , as they lay a lower proportion of fertilised eggs following a single copulation in comparison with less productive females [ 38 ] . without measures of paternity however , the value of both mate choice and multiple mating can only be inferred indirectly .

with eyes at the tip of their eye stalk , teleopsis dalmanni and members of diopsinae definitely make into the list of most bizarre - looking animals on earth . this group of flies has sparks research interest in the physiology , development and evolutionary mechanism leading to the eye stalks . t . dalmanni is probably the most widely studied particularly in the field of sexual selection leading to sexual dimorphism in this species , where males and females differ in appearance .

the fly , c . dalmanni , is highly promiscuous ( wilkinson et al . , 1998 ) thereby creating ample opportunity for intense postcopulatory sexual selection by sperm competition or selection . comparative studies across stalk - eyed flies reveal that sperm length , spermathecal duct length and ventral receptacle size have coevolved between males and females ( presgraves et al . , 1999 ) . the size and shape of female sperm storage organs have the potential to influence which sperm are used for fertilization . thus , correlated evolution between male and female reproductive traits may be due , in part , to selection on sperm size mediated by the size of the female organs . however , correlated evolution between male and female reproductive traits may also be the result of linkage disequilibrium between pre - and postcopulatory traits . among lines selected for long or short male eye span , wilkinson et al . ( 2005 ) found a strong correlation between eye span and ventral receptacle size due , in part , to x - linked effects . eye span is , therefore , partly indicative of both male and female postcopulatory features . consequently , genetic linkage among x - linked genes that influence eye span , sperm length and ventral receptacle size provides a mechanism by which female mate choice can potentially influence male external morphology and sperm length as well as result in coevolution between sperm length and female sperm storage organ size . furthermore , the genetic linkage between eye span and sperm length allows both pre - and postcopulatory sexual selection to act against the transmission bias caused by the sex - ratio chromosome .

lay on average 4 - 6 eggs per day and may continue laying eggs for many months . the eggs require 1 - 3 days to hatch . larvae stage range from 10 days to several weeks , depending on temperature of environment and food quality . late - instar larvae empty their gut content in a process called gut - purge , and enter pupation state . in food - depriving environment , pupation might occur at smaller larvae size . they typically pupate on emergent vegetation . pupation stage last for almost a week , after which an adult fly will emerge , completing the life cycle of

as yet , there has been no effort to identify within - population quantitative variation in p 2 in stalk - eyed flies . in this paper we investigated intra - specific , within population variation of p 2 in t . dalmanni using controlled mating experiments and microsatellite profiling of progeny . we standardized male mating history , diet and body size in order to limit variation in male reproductive organ size , as we have shown that testes and accessory glands are reduced by mating [ 41 ] and scale positively with diet quality and body size [ rogers et al . in prep ; cotton & pomiankowski unpublished ] . we also chose sires with similar eyespan to each other to limit the potential effects on p 2 of female mate choice based on male ornament size [ 25 , 27 , 28 ] . we show that even in the absence of these factors there is significant variation in sperm precedence in t . dalmanni , with familial p 2 values ranging from zero to one . we discuss the likely causes of this variation .

we know that sperm precedence in c . dalmanni is highly variable and exhibits a trimodal distribution ( corley et al . , 2006 ) . furthermore , when females are double - mated to st and sr males , st males are twice as likely to fertilize offspring ( wilkinson et al . , 2006 ) . the greater sperm length of st males may facilitate fertilization success . in other insect species , longer sperm do not necessarily have a fertilization advantage over shorter sperm ( e . g . , gage and morrow , 2003 ) , but can in species where females mediate fertilization through organs like sperm receptacles ( reviewed in snook , 2005 ) . we do not know the exact mechanisms of sperm competition in c . dalmanni ; there may be a trade - off between producing many small or few long sperm , although very few sperm per ejaculate succeed in getting stored in female spermathecae ( approximately 35 in cyrtodiopsis whitei ; fry and wilkinson , 2004 ) . male and female postcopulatory traits have coevolved across stalk - eyed fly taxa ( presgraves et al . , 1999 ) and are the fastest evolving traits measured among populations within c . dalmanni ( eg amitin and gs wilkinson , unpublished data ) , which are patterns consistent with sperm competition mediated by ventral receptacles . double - mating experiments using flies that differ only in sperm length , but not presence of drive , are needed to determine how sperm length influences sperm competitive ability . by simultaneously allowing males to differ in eye span it may be possible to determine whether pre - and postcopulatory selection operates in concert or independently on male pre - and postcopulatory sexually selected traits .

templeton ( 26 ) proposed that sexual selection is not important in speciation in the hawaiian drosophila because mate choice is stabilizing within species . the sexually selected trait that we examined is not important in behavioral isolation , but the reason is not consistent with templeton’s proposal because we found directional sexual selection through female mate choice . our detection of directional selection is not due to sampling a smaller size range than templeton did because the range of head widths in our study was 2 . 4–3 . 1 mm , nearly the same as the range studied by templeton ( 17 , 26 ) . statistical analyses of selection are essentially correlational ( 25 , 29 ) , and the cause of selection needs to be confirmed with an experimental approach , such as increasing the male eye span through artificial selection ( 30 ) . female preferences for broad heads in distantly related stalk - eyed flies ( diopsidae ) also appear to be directional ; females preferred to perch near males with heads that had been widened experimentally well beyond the natural range of the species ( 31 ) .