Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a serious pest of greenhouse vegetable and ornamental crops across Canada (Broadbent et al. 1987). Upon completing larval development, F. occidentalis either pupates on their host plant or drops to the ground before pupation occurs (Lewis 1973). Because several soil-dwellers prey on or infect F. occidentalis pupae (Gillespie and Quiring 1990; Helyer et al. 1995), assessing the proportion of individuals that pupate on the ground is of critical importance for developing pest management strategies. The present study provides the first quantitative assessment of the pupation behaviour of F. occidentalis.