Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2002
Publication Date: N/A
Interpretive Summary: Whiteflies are major agricultural pests with worldwide distribution. Encarsia formosa, a tiny parasitic wasp, has been used successfully for many years to control whiteflies in greenhouses, yet little is known about the behavior and development of the immature wasp within its whitefly host. We have studied the development of Encarsia formosa within the greenhouse whitefly using light microscopic techniques. We found that the adult wasp lay their eggs within the nervous system of the whitefly, perhaps to avoid host defense mechanisms. The parasites were found to coordinate their own development with that of the whitefly so that they never progress to their final immature stage until the whitefly initiates its own adult development. Our results suggest that the wasp larvae can sense the hormones that trigger the adult development of the whitefly. We describe physical characteristics of the immature wasps that will allow other researchers to identify specific stages of wasp development in future studies. This study will be valuable to scientists studying the developmental physiology of parasitic wasps, and will be of use in future attempts to develop artificial rearing systems for the mass production of parasites for biological control.
Technical Abstract: 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 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.