Adult coccinellid activity and predation on aphids in spring cereals

Improved understanding of coccinellid activity and predation on aphids in t he field could clarify their potential in aphid biological control, Our obj ective was to determine the influence of abiotic and biotic factors on acti vity and predation by adults of three coccinellid species (Hippodamia conve rgens Guerin-Meneville, H. tredecimpunctata tibialis (Say), and Coleomegill a maculata DeGeer) in spring cereal fields. The proportion of time coccinel lids spent searching was correlated with air temperature, aphid density, an d time of day. The relationship between searching and these variables diffe red among species. Mean walking speed ranged from 66.4 cm/min for C. macula ta to 83.2 cm/min for H. tredecimpunctata and increased with temperature fo r all species. The frequency of short flights (<2 m) by beetles increased w ith temperature and decreased with increasing aphid density for all species , but the relationship of short flight frequency to these variables differe d among species. The frequency of long flights (>2 m) was similar for all s pecies and influenced by temperature and calendar date. The frequencies wit h which aphids were encountered and eaten were correlated with aphid densit y and temperature for H. convergens and H. tredecimpunctata. Despite over 2 50 h spent observing adult coccinellid behavior in the field, predation dat a were insufficient to develop a useful predation model.