VARIATION IN DIAPAUSE AND SEX-RATIO IN THE PARASITOID ASOBARA-TABIDA

Asobara tabida Nees (Hymenoptera: Braconidae) is a widespread parasito id, attacking larvae of Drosophila (Diptera: Drosophilidae) species in fermenting substrates. In this species, geographic variation is found in the percentage of parasitoids entering diapause and in the sex rat io of emerging parasitoids. Percentage diapause appears to be influenc ed by host species (more parasitoids enter diapause in D. melanogaster Meigen than in D. subobscura Collin) and temperature. It is not corre lated with any of the abiotic factors investigated, but is correlated with survival probability in D. melanogaster larvae and with the time of year in which the experiment was conducted (even though none of the parasitoids experienced natural day light). Sex ratio was only found to correlate with percentage diapause, suggesting that males enter dia pause more frequently than females. It is concluded that A. tabida use s diapause to survive both unfavourable abiotic and biotic circumstanc es.