Effect of host plant on body size of Frankliniella occidentalis (Thysanoptera : Thripidae) and its correlation with reproductive capacity

The effect of different host plants on Frankliniella occidentalis (Pergande ) (Thysanoptera: Thripidae) body size was investigated. Thrips from three d ifferent populations, from the Netherlands, Italy, and USA, achieved greate r body sizes when reared on cucumber than on bean. The same thrips grew lar ger when reared on susceptible than on resistant cucumber. On the latter, r eproduction was reduced, suggesting that smaller thrips have a lower reprod uction. However, no evidence was found for a correlation between size and r eproduction in experiments with thrips from four different populations, fro m the Netherlands, New Zealand, France, and USA that differed significantly in body size. Also when individual thrips from the four populations were t ested, there was no correlation between size and reproduction. It is conclu ded that resistant cucumber affects both size and reproduction off. occiden talis. However, lower reproduction in general is not associated with smalle r body size.