The predators of insects

Abstract. 1. Insect–insectivore trophic relations were reviewed using presence–absence data from sixty-one invertebrate-dominated food webs and fifteen food webs from Briand's (1983) original forty web collection. From counts of prey links in higher taxa (orders, classes, phyla), six phyla and thirteen classes of non-insect insectivores and fourteen orders of insect predators and prey were found. 2. Detritus-based habitats (phytotelmata, felled logs, carcasses, dungpads) harboured fewer orders of insects, that interact with other insects, than webs from grazer-based (host plants, some galls) and mixed-based systems (aquatic webs). Consumer–resource networks of higher insect taxa in these webs shared several features found in some species-level biological networks: the trend was towards few pairs of strong asymmetrical links, several weak links and many null interactions. 3. From counts of insect predator–insect prey links, hymenopterans as terrestrial predators and parasitoids interacted with the most number of higher insect taxa. Hymenopterans were also linked as prey more often than other terrestrial insects. In freshwater habitats, plecopterans were linked as predators more often than other aquatic taxa, whereas dipterans were listed as prey more often than other insects. 4. Dipterans were linked in the diets of non-insect insectivores from seven of eight common taxonomic classes. Arachnids were identified as insect predators by food web researchers in the largest number of webs, followed by passerine birds and cyprinodont fishes. From analysis of prey links at the ordinal level, predaceous insects were less polyphagous than other predators (other ectotherms and endotherms). 5. Analysis of chain lengths, as expected, showed that insect prey occupied mostly lowermost trophic levels, non-insect insectivores were found mostly at uppermost trophic levels, and predaceous insects were found mostly at intermediate trophic levels across most habitats. 6. This analysis offers evidence that insects are not just occupying intermediate trophic levels in some communities. Indeed, some taxa feed at the upper ends of long food chains, for example eupelmids in galls, staphylinids in carcasses, and perlid plecopterans in streams.