The distribution and movement of apterous Myzus persicae on rapidly growing turnip plants

Abstract. 1. The spatial distribution of both adult apterous and nymphal M.persicae was related to the “age” of the leaf. 2. This distribution was bimodal and was maintained even on rapidly “ageing” leaves by frequent emigration. 3. The spatial distribution was also found to change between regions of a leaf, the densest populations occurring at the base of all leaves, but with the populations most evenly distributed on the young and old leaves. 4. The spatial distribution also changed during the nymphal period, the youngest nymphs being found predominantly on the lamina, the fourth instar and adults on the largest available veins. 5. On rapidly growing plants, individual M.persicae may move to a new feeding site as frequently as every 24–48 h. 6. Some of the causes and consequences of this frequent dispersal are discussed.