Insect Fauna Associated With Anacardium occidentale (Sapindales: Anacardiaceae) in Benin, West Africa
ABSTRACT. Cashew, Anacardium occidentale L. (Sapindales: Anacardiaceae), is an important cash crop in Benin. However, its production is threatened by several biotic factors, especially insects. In Benin, very few studies have focused on insects and just listed species commonly found on cashew worldwide. The present investigation fills this gap by presenting an exhaustive inventory of insect species associated with this crop in the country. The survey was carried out from September 2009 to August 2010 in 22 cashew orchards (5 young and 17 mature) distributed over three major agroecological zones where cashew is most produced in the country. Insects were collected using chemical knock-down technique and visual observation followed by capture with sweep net. In addition, infested plant organs were sampled and incubated to collect emerging insects. In total, 262 insect species were recorded and identified. Among them, the wood borer Apate terebrans Pallas, the leafminer Eteoryctis gemoniella Stainton, and the mirid bugs Helopeltis schoutedeni Reuter., and Helopeltis anacardii Miller., appeared as the most important insect species attacking cashew in Benin. Beneficial insects encountered included some predators, parasitoids, and pollinators. Few vertebrate predators were also recorded on the trees. Differences in agroecological conditions or in field cleanliness did not affect the number of insect species encountered in the cashew orchards. The results of this study represent an important baseline data for the design and implementation of strategies for cashew protection in Benin.
Adaptation d'Oecophylla longinoda [Formicidae-Formicinae] aux variations spatio-temporelles de la densité de proies
RésuméL'activité prédatrice de 12 sociétés d'Oecophylla longinoda Latreille a été étudiée durant 124 h d'observations pendant lesquelles 2 482 proies ont été capturées. La prédation s'exerce sur les arbres supportant les nids ainsi que sur des territoires «secondaires» habituellement situés sur le sol. Les 7 situations suivantes sont comparées: 1) En forêt, durant les périodes «habituelles»; 2) Durant le passage d'une colonne de Magnans; 3) Le territoire de chasse «secondaire» d'une société installée sur un arbre situé en bordure de rivière correspond à une zone où de nombreux insectes se concentrent pour s'abreuver; 4) L'arbre support est un manguier dont on suit le cycle biologique (inter-saison, floraison, fruits mûrs) et son impact sur la prédation par lesOecophylla; 5) On compare la situation «habituelle» à ce qui se passe lorsqu'un essaimage de Termites est rabattu sur les territoires d'une société; 6) Le territoire «secondaire» est situé sous la véranda d'une maison éclairée chaque nuit où de nombreux insectes ailés sont attirés; 7) Les territoires «secondaires» de 2 sociétés étant contigus, on compare les périodes de combats aux périodes calmes.Les territoires «secondaires» sont situés sur des zones de concentration en proies (insectes de la litière des forêts, zones où ils viennent s'abreuver, attraction par la lumière, la nuit). LesOecophylla y capturent souvent des insectes aptères, cas relativement rare sur l'arbre support. Ces territoires sont défendus contre les ouvrières d'autres sociétés.Du fait de leur territorialité très marquée avec surveillance permanente du territoire et un recrutement très efficace, lesOecophylla répondent très rapidement à toute prolifération en proies. A cela s'ajoute une grande diversité de proies potentielles de sorte que cette espèce peut être considérée comme très efficace en lutte biologique, les ouvrières réagissant spécifiquement à toute abondance d'un type d'insecte.Pour une société comprenant 12 calies, le nombre de proies capturées par an est de l'ordre de 45 000. Ramené à un nombre équivalent d'individus et de jours d'activité, il est du même ordre que celui desFormica lugubris (Cherix, 1986).SummaryThe predatory activity of 12 societies ofOecophylla longinoda Latreille was observed for 124 hours during which 2,482 prey items were captured. Predation took place in trees containing the nests (“habitual” territory) and in “secondary” territories usually situated on the ground. The 7 following situations were observed. Ant activity I) In the “habitual” tree situation; 2) During the passage of a column of Dorylinae; 3) In the “secondary” hunting territory of a society settled on a tree close to the bank of a river; a zone where numerous insects gathered to drink; 4) In a society centred on a mango tree in which the biological cycle (seasonal variations, blossoming time, fruit ripening) and its impact on predation byOecophylla was closely observed; 5) In a “habitual” situation when a swarm of fermites fell into the territory of a society; 6) In a “secondary” territory situated beneath a house verandah, to which numerous winged insects were attracted each night by the verandah light; 7) In the “secondary” territories of two contiguous societies during both the combat and the calm periods.“Secondary” territories are generally situated in zones, such as on the forest floor, along side water courses or beneath lights where there is a concentration of prey. At such sites,Oecophylla often capture wingless insects which they rarely catch on trees.Due to their pronounced territoriality, permanent surveillance and very efficient recruitment,Oecophylla respond extremely quickly to any increase in prey numbers. Owing to the great diversity in their potential prey, this species can be considered very effective as a biological control agent. For example, a society comprising 12 nests will capture about 45,000 prey items per year. When corrected for the numbers of individuals involved and the period of activity, the predation level of this species is similar to that ofFormica lugubris.
Observations on the insect fauna of shaded and unshaded Amelonado cocoa
Abstract The insect fauna of a block of Amelonado cocoa trees at Tafo, Ghana, partly shaded by Gliricidia sepium and partly unshaded was sampled. Crematogaster clariventris (Mayr) and Oecopyhlla longinoda (Latr.) were the most numerous species of ants, the former occurring on 84% of the trees and the latter on 17%. There was a considerable overlap in the distribution of the two species. Thirty-two other species of ant were collected by pyrethrum knockdown sprays from the cocoa canopy, and 47 species were collected from leaf litter beneath the trees. More species of ant were recovered from litter on shaded plots than on unshaded ones. There was some avoidance of trees occupied by O. longinoda by certain canopy .ants. A greater number of Lepidoptera larvae, Orthoptera and the mirid Sahlbergella singularis Hagl were collected by pyrethrum knockdown sprays from unshaded plots than from shaded ones, whereas Diptera and Hymenoptera other than ants were more numerous on shaded plots. The most abundant coccid was Stictococcus sjostedti Ckll., a species tended for its honeydew by both dominant ants; it was more common on shaded plots. Mealybug species, of which Planococcoides njalensis (Laing) was the most common, were more abundant on unshaded plots.