Abstract: The western flower thrips, Frankliniella occidentalis (Pergande), has successfully settled down in parts of Beijing vegetable production areas and damaged a lot of vegetables. In order to understand the spatial distribution patter of this pest, its population aggregating indexes on cucumber and green bean were calculated based on the related index formulae, and Taylor and Iwao regression formulations. The results showed that the spatial distribution pattern of the western flower thrips belonged to aggregating distribution on cucumber and green bean. Differences in sampling time and population densities had no effect on the spatial distribution pattern of F. occidentalis. Analysis of population dynamics showed that adults and larvae of the thrips mostly were feeding on middle leaves of cucumber (the number of thrips on 4th to 17th leaf was higher than that on other leaves), and that thrips caused lighter damage to unfold leaves, the younger and the older leaves. Theoretical sampling within allowable error by α and β based on Iwao regression formulation was measured.

Key words: Frankliniella occidentalis, spatial distribution pattern, aggregating distribution, theoretical sampling