Population estimates and dispersal of Hydrotaea irritans Fallén

Abstract. 1. Population estimates of Hydrotaea irritans were made by a mark and recapture technique at one site from 1976 to 1978.
2. Population densities of five to 200 thousand ha^-1 were found with large-scale immigration and emigration occurring from the site.
3. The dispersal of marked adults from a point of release was rapid and marked flies were captured up to 3 km from the release point.
4. The distribution of flies along a woodland strip was not homogeneous; certain areas appeared to be more attractive and held more flies over a period of time.
5. The importance of the increasing area within which flies may be found as they move outwards from the release point is discussed.