Life histories and host specificities of theEchium flea beetlesLongitarsus echii andL. Aeneus [Col. Chrysomelidae]
Two halticine flea beetles,Longitarsus echiiKoch andLongitarsus aeneusKutsch, occurring on the boraginaceous plantEchium plantagineum L. in the western Mediterranean region are potential biological control agents in Australia where the plant has become a weed (Paterson's curse). The adults of both species feed by making “shot holes” in the leaves. The larvae of both species attack the roots ofEchium, those ofL. echii feeding more centrally in the root than those ofL. aeneus which attack the outer cortex and rootlets. Both species are univoltine. The host restrictions of both flea beetles as adults and as larvae were tested using the criteria already established for theEchium leaf minerDialectica scalariellaZeller (Wapshere & Kirk, 1977). This testing established that it would be safe to introduce the 2 insects into Australia for the biological control ofE. plantagineum and they are now under quarantine.RésuméDeux altises,Longitarsus echiiKoch etLongitarsus aeneusKutsch, vivant surEchium plantagineum L. dans l'ouest de la région méditerranéenne, sont des agents de contrôles biologiques potentiels de cette adventice en Australie. Les adultes des 2 espèces creusent des trous dans les feuilles et leurs larves attaquent les racines de la plante. Les larves deL. echii se nourrissent plus de la partie centrale de la racine, alors que celles deL. aeneus préfèrent le cortex extérieur et les radicelles. Les 2 espèces ont une génération par an. La spécificité d'hôte des 2 espèces, tant adultes que larves, a été étudiée selon les critères déjà établis pourDialectica scalariellaZeller (Wapshere & Kirk, 1977). Ces essais ont confirmé que l'introduction des 2 insectes en Australie pour la lutte biologique contreEchium plantagineum serait sans danger, et cette introduction a eu lieu récemment.
Natural impact of the flea-beetle, Longitarsus sp., on Heliotropium amplexicaule in Argentina and its potential for use as a biological control agent in Australia.
Heliotropium amplexicaule (Boraginaceae) was introduced into Australia from South America over 100 years ago and has since become a serious weed in summer pastures. In 1998, CSIRO started a classical biological control project against H. amplexicaule to search for and evaluate natural enemies in its native range in Argentina. This study quantifies the impact of one such natural enemy, the fleabeetle Longitarsus sp. (Coleoptera: Chrysomelidae), on H. amplexicaule, to determine its potential for control of the weed in Australia. Longitarsus sp. adults chewed small feeding holes in the leaves of H. amplexicaule plants, leading to necrosis and death of the remaining leaf tissue. Feeding started from the basal leaves, with new leaves attacked as they developed on the growing plants. Unattacked control plants achieved maximum size by early March. The mean growth of attacked plants at the two attacked sites was only 54 and 48%, respectively, of that shown by these control plants. Moreover, these plants showed greatly reduced vigour and half of them had died by mid-March at one site and mid-May at the other. There was no plant mortality at the control site. Finally, control plants produced significantly larger quantities of flowers and seed over a longer period than did attacked plants. The overall impact of Longitarsus sp. is due to a combination of adult feeding on leaf tissue and larval feeding on the root system. The study also demonstrates a synergism between the flea-beetle and pathogenic micro-organisms causing subsequent leaf necrosis. Such impact on plant survival and reproductive potential suggests that Longitarsus sp. could be a good biological control agent for H. amplexicaule in Australia, provided it demonstrates sufficient host specificity.
The relation of food quantity to rumination behavior.
Preliminary work suggested that the quantity of food ingested by retarded individuals who usually ruminated following meals was related to the frequency and duration of ruminating responses. This possible relation was experimentally examined by systematically varying food quantity from regular portions to satiation levels for three retarded individuals who exhibited high levels of ruminating. A clear functional relation of food quantity to ruminating emerged, with satiation procedures producing rapid and large decreases in the relatively high frequencies and durations of ruminating characteristic of baseline food quantity conditions.