Arthropods in cereal crops: nocturnal activity, vertical distribution and aphid predation.
As part of a wider study on the ecology of cereal crops, preliminary studies were carried out in Britain on the nocturnal activity and vertical distribution of some arthropods in cereal crops. In 1973, vacuum and sweep net samples were taken from spring barley and sweep samples from winter wheat at regular intervals throughout a 24 h cycle. In 1974, sweep net samples were taken from spring barley and winter wheat and the ground zone fauna was sampled with a pooter. In both 1973 and 1974 the gut contents of arthropod predators sampled were examined for aphid remains. In 1974 the precipitin test was also used to detect feeding on aphids. In 1973, large differences were found between arthropod taxa present in vacuum and sweep net samples taken at different times of the 24 h cycle. The largest differences were in the numbers of Thysanoptera and Coleoptera. More Thysanoptera were found during the day and more Coleoptera at night. More polyphagous predators were found in vacuum and sweep net samples at night in 1973. A similar pattern was evident in 1974. In both 1973 and 1974, many of the polyphagous predators, including Staphylinidae, Carabidae, Dermaptera and Araneae, fed on aphids. More polyphagous predators fed on aphids at night. For example, 17% of the predators from vacuum samples taken at 3 p.m contained aphids, as compared with 67% at 3 a.m.