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 arthropod predators in agro-ecosystems. Differences in the quality of available species may play a significant role in the build-up of a community of natural enemies. The value of some common epigeic and hemi-edaphic Collembola as prey for adults and larvae of the carabid beetle Bembidion lampros was assessed in laboratory experiments. 2. Consumption capacity, egg production and the efficiency of converting prey into eggs were used as quality criteria for beetle adults, kept on diets of the collembolans Isotoma anglicana, Isotoma notabilis, Isotomurus prasinus, Folsomia fimetaria and Lepidocyrtus cyaneus, with fruit flies Drosophila melanogaster used as a high quality comparison prey. Survival, developmental 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 declined over time on all collembolan diets, indicating a lower quality of all species compared with D. melanogaster, but there was considerable variation between species. The highest food conversion efficiency occurred on F. fimetaria, 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 two Collembola seemed to be of relatively higher quality for larvae than for adults. Significantly higher teneral weight occurred on a diet of D. melanogaster compared with the Collembola. 6. The effect of Collembola quality on the beetle fecundity and larval developmental time suggests that agricultural management for natural enemies, should aim to benefit the species composition of the prey population.