INDUCTION OF MALES IN THE THELYTOCOUS WASP ENCARSIA-FORMOSA GAHAN (HYMENOPTERA, APHELINIDAE)

The thelytokous wasp Encarsia formosa Gahan Is widely used as an agent for biological control of the greenhouse whitefly Trialeurodes vaporariorum (West-Wood) In greenhouses in central and northern Europe (Van Lenteren And Woets, 1988). The mechanisms of male appearance in this parasitoid have not been fully explained (Kajita, 1989). Some authors stated that E. formosa males are hyperparasitoids (Gerling, 1966; Flanders, 1967), while others reported that the males develop as primary parasitoids (Vet And Van Lenteren, 1981). In addition, it is almost universally believed that low greenhouse temperatures precede the occurrence of males in E. formosa (Speyer, 1927). However, it has been known that high temperatures also induce the occurrence of males in several parasitoid species (Flanders, 1965; Gordh And Lacey, 1976). More recently, Stouthamer Et al. (1990) showed that thelytokous Trichogramma species can be rendered arrhenotokous by exposure to high temperatures or certain antibiotics. This paper reports that E. formosa females exposed to high temperatures or certain antibiotics can produce male offspring, which develop as primary parasitoids of the greenhouse whitefly. © 1993, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.