H. Sadeghi - Department of Plant Protection, College of Agriculture, Ferdowsi University, Mashhad Islamic Republic of Iran.

The relationship between female oviposition preference and offspring performance is a key area of study on the evolution of host specificity. This study investigates host prefer-ence of the polyphagous hover fly Syrphus ribesii (Diptera: Syrphidae) and compares it with some components of its offspring`s performance. Females and offspring were tested on six naturally used aphid hosts (blackberry, dock, nettle, pea, rose, and sycamore aphids). In the laboratory, larvae were able to develop successfully on aphids which were rarely selected for oviposition by gravid females. Despite the relatively small differences in performance resulting from feeding on different aphids, there was evidence for a pref-erence-performance correlation in the generalist S. ribesii.

Host choice, Host specificity, Fitness, Preference-performance