DISPERSAL OF A GALLING SAWFLY - IMPLICATIONS FOR STUDIES OF INSECT POPULATION-DYNAMICS

1. Utilizing population censuses and field experiments we investigated the dispersal behaviour and the role that dispersal plays in the popu lation dynamics of the shoot-galling sawfly Euura lasiolepis. 2. Activ e, non-directional dispersal occurred out to 8 m, was strongly female biased (88% female) and relatively common (92% of dispersing sawflies) . Passive, wind-directed dispersal occurred out to 128 m, was not fema le biased (56% female, the same sex ratio as emerging sawflies) and re latively rare (8% of dispersing sawflies). 3. Dispersal was density-in dependent but increasing density decreased the number of galls per ind ividual initiated by non-dispersers. 4. Life-table analysis was used, including field survivorship and sex ratio data, to model the role dis persal can play in the population dynamics of this sawfly. 5. We concl ude that direct evaluation of both immigration and emigration should b e included in life-table analyses to more fully understand insect popu lation dynamics.