Aphid Feeding by Some Polyphagous Predators in Relation to Aphid Density in Cereal Fields

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Abstract
Samples of aphids and predators were taken from 10 spring barley and winter wheat fields between May and Sept. 1972-1977. The guts of .apprx. 12,00 predators were dissected and the presence or absence of aphid remains recorded. Sixteen species of Carabidae, 3 spp. of Staphylinidae and 1 sp. of earwig fed on aphids. No relationship was found between the amount of feeding and aphid densities in the different years. When the species were considered separately, the proportion containing aphid remains increased with aphid density, although the form of this relationship varied between species. Tachyporus spp. had a limited response to aphid density; Amara plebeja, A. aenea and Notiophilus biguttatus ate aphids only at higher aphid densities. Forficula auricularia, Agonum dorsale and Demetrias atricapillus were the most important, both in terms of the overall percentage containing aphid remains, and the predation index (proportion containing aphid remains during the aphid increase phase multiplied by the mean density of the predator at this time). These 3 spp. should be the most valuable in restricting build-up of aphids. Successful aphid predation at low aphid density may be partly related to the climbing ability of the predator.