The diet of some predatory arthropods in cereal crops.
The gut contents of 1206 arthropods of 26 species collected from pitfall traps in cereal crops in southern England in 1973 were examined under a binocular microscope. Fifteen taxa, mostly Staphylinidae, had no solid remains in the gut and were probably fluid-feeders. Notiophilus biguttatus (F.), Loricera pilicornis (F.) and Lamyctes fulvicornis Meinert fed primarily on Collembola, Tachyporus spp. on fungi, Agonum dorsale (Pontoppidan) on aphids, Forficula auricularia L. on plant material and Bembidion lampros (Hbst.) on Diptera and Collembola. Pterostichus (Feronia) melanarius (Ill.), Harpalus rufipes (Deg.) and Nebria brevicollis (F.) contained a wide range of food, and there was considerable overlap between species, but Coleopterous adults and larvae featured prominently in the diet of all three. Aphids were eaten by seven species and formed an appreciable part of the diet of A. dorsale and Forficula auricularia. The list of aphid feeders was extended to 12 species by the examination of a further 1051 insects collected by daytime search of the ground zone of a spring barley crop. The importance of A. dorsale as an aphid feeder was confimed and Demetrias (Risophilus) atricapillus (L.), Calathus fuscipes (Goeze), T. chrysomelinus (L.), Amara familiaris (Duftschmid) and N. brevicollis were also shown to have fed on aphids. For B. lampros and Tachyporus spp. the percentage containing food was higher for non-gravid females than for males or gravid females, whilst in P. melanarius and Agonum dorsale both gravid and non-gravid females had a higher percentage than males. It is suggested that the efficiency of these species as potential agents of natural control could be influenced by their sex ratio and time of breeding in relation to the timing of critical periods in the cycle of pest abundance.