SITE-SPECIFIC EFFECTS OF PARASITISM ON WATER-BALANCE AND LIPID-CONTENT OF THE PARASITIC WASP NASONIA-VITRIPENNIS (HYMENOPTERA, PTEROMALIDAE)

The site of parasitism on a host selected by the ectoparasitic wasp Na sonia vitripennis affected the water composition of developing larvae. Second instar wasp larvae developing on anteriorly-parasitized pharat e adults of Sarcophaga bullata contained 12% more water by mass than w asps feeding on the posterior end of the fly. Similar differences, alt hough less pronounced, were detected in third instar larvae and are at tributed to a greater dry weight (fat). Regardless of the amount of fa t present in wasp larvae, rates of water loss and oxygen consumption w ere the same. This suggests that variation in parasitoid fat content d id not contribute to water conservation. Parasitism resulted in an ele vation in the hemolymph and fat body lipid content of Salcophaga bulla ta, but the induced-hyperlipaemia was most pronounced in posteriorly-p arasitized flies. Wasp larvae reared on the latter type of host contai ned the most extractable lipid, implying that variation in parasitoid Eat content simply reflects differences in host composition. Differenc es in the quantity of host lipids did not alter the duration of parasi toid development.