Co-development of Encarsia formosa (Hymenoptera: Aphelinidae) and the greenhouse whitefly, Trialeurodes vaporariorum (Homoptera: Aleyrodidae): a histological examination.

Using histological techniques, we have simultaneously examined the co-development of the Aphelinid parasitoid Encarsia formosa and its host the greenhouse whitefly, Trialeurodes vaporariorum. Previously we have determined that regardless of the whitefly instar parasitized, parasitoid larvae would not molt to their final instar until the whitefly reaches its maximum dimensions. In unparasitized T. vaporariorum, this point in development corresponds to the initiation of the adult molt. In part, this study was conducted to determine the developmental state of parasitized whiteflies at the time they achieve their maximum dimensions. It was found that parasitized final instar T. vaporariorum do, in fact, undergo a final molt and that E. formosa larvae will not molt to their final instar until this has occurred. The timing of the final whitefly molt appears unaffected by parasitization. The commonly observed melanization of parasitized whiteflies appears to be a consequence of this molt. In addition, we have discovered that the adult wasp oviposits within the ventral ganglion of the whitefly, and that major organ systems of the whitefly persist very late into parasitoid development. We also report the presence of possible endosymbiotic bacteria residing in the fatbody of E. formosa.