The value of Collembola from agricultural soils as food for a generalist predator

1. The Collembola is one of the important prey groups for generalist arthro pod predators in agro-ecosystems. Differences in the quality of available s pecies may play a significant role in the build-up of a community of natura l enemies. The value of some common epigeic and hemi-edaphic Collembola as prey for adults and larvae of the carabid beetle Bembidion lampros was asse ssed in laboratory experiments. 2. Consumption capacity, egg production and the efficiency of converting pr ey into eggs were used as quality criteria for beetle adults, kept on diets of the collembolans Isotoma anglicana, Isotoma notabilis, Isotomurus prasi nus, Folsomia fimetaria and Lepidocyrtus cyaneus, with fruit flies Drosophi la melanogaster used as a high quality comparison prey. Survival, developme ntal time and teneral adult weight were used as quality criteria for beetle larvae on diets of Isotoma anglicana, Isotoma notabilis, F. fimetaria, D. melanogaster and a starvation treatment. 3. Collembola were offered to adults in dead and live treatments to assess the cost of prey capture and handling in relation to prey quality. 4. Bembidion lampros ate more dead than live Collembola. Egg production dec lined over time on all collembolan diets, indicating a lower quality of all species compared with D. melanogaster, but there was considerable variatio n between species. The highest food conversion efficiency occurred on F. fi metaria, L. cyaneus and D. melanogaster, while Isotoma notabilis could not be utilized by B. lampros for egg production. 5. Larvae completed development with low mortality on Isotoma anglicana and F. fimetaria, although there were differences in developmental time. The t wo Collembola seemed to be of relatively higher quality for larvae than for adults. Significantly higher teneral weight occurred on a diet of D. melan ogaster compared with the Collembola. 6. The effect of Collembola quality on the beetle fecundity and larval deve lopmental time suggests that agricultural management for natural enemies, s hould aim to benefit the species composition of the prey population.