Predation of a chrysomelid beetle (Gastrophysa polygoni) in cereals by polyphagous predators.
Gastrophysa polygoni (L.) (Coleoptera: Chrysomelidae) feeds on species of the genus Polygonum e.g. knotgrass (Polygonum aviculare L.) and black bindweed (Polygonum convolvulus L.) found in cereals. G. polygoni overwinters in the soil in the adult stage and emerges in the spring. The first eggs are usually found in early May, reaching a peak 3 or 4 wk later. The yellow eggs are laid in batches of about 20 on the undersides of the leaves. On hatching, the first-instar larvae feed upon any infertile or unhatched eggs in the batch and then tend to remain feeding on the plant on which the egg batch had been laid. The more mobile second- and third-instar larvae may feed on different plants. Once fully fed, third-instar larvae leave the plant and enter the soil where they pupate. There are usually two generations each year. Further information on the biology of G. polygoni may be found in Sotherton (1980).