Induction of males in thelytokous populations of Encarsia meritoria Gahan and Encarsia protransvena Viggiani (Hymenoptera: Aphelinidae): a systematic tool.

Males from thelytokous females of Italian uniparental populations of Encarsia meritoria and Encarsia protransvena were obtained by feeding wasps with tetracycline orrearing parasitoids at high temperatures respectively. Two thermic treatments were tested on E. protransvena: 31°C constant temperature versus an alternation of 12 hours at 33°C and 23°Con a daily basis. Females of E. meritoria fed with tetracycline produced 80.87% of male progeny. Tetracycline did not induce male offspring in E. protransvena. For this species high temperatures were required even though only a few males were obtained (0.31–5.43%). These results confirm the infection of parthenogenesis-inducing micro-organisms in E. meritoria, while this is doubtful in E. protransvena. Males derived from the lytokous populations of the two species were described. Males of the uniparental population of E. meritoria were similar to those of biparental ones, suggesting that the two populations are conspecific. Males of E. protransvena are slightly different from those described previously, supporting the hypothesis that E. protransvena is a complex of cryptic species. Our results suggestthe possibility of using ``induced males'' by either antibiotics or high temperatures as a taxonomic tool in the genus Encarsia to separate similar (if not undistinguishable) uniparental species.