Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

After newly hatched Manduca sexta larvae were parasitized by Apanteles congregatus, the wasps emerged from third, fourth, fifth, or supernumerary sixth stage host larvae. The number of parasites present within a host determined the time required for Apanteles development and the final host instar. In addition, the percent of parasites within a host which successfully completed their development and emerged was determined by the parasite load. Parasitized larvae gained weight more slowly and attained lower final weights than did unparasitized control larvae; this was attributed to reduced food consumption by the parasitized larvae. Following parasitization of freshly ecdysed fifth‐instar Manduca larvae, the rate of Apanteles development was accelerated with respect to that observed when young larvae served as hosts. Parasitism also induced developmental changes in Manduca larvae which encapsulated Apanteles and from which no parasites emerged. Our findings suggest that such larvae retain high juvenile titers late in larval life, preventing normal metamorphosis. ZUSAMMENFASSUNG WECHSELWIRKUNGEN BEI DER ENTWICKLUNG DES TABAKSCHWÄRMERS, MANDUCA SEXTA, UND SEINES PARASITEN, DES BRACONIDEN APANTELES CONGREGATUS Nachdem frischgeschlupfte Manduca sexta Raupen durch Apanteles congregatus parasitiert worden waren, schlüpften Wespen aus dem dritten, vierten, funften oder aus einem überzähligen sechsten Raupenstadium des Wirts. Die Zahl der Parasiten in einem Wirt bestimmte die für die Entwicklung von Apanteles erforderliche Zeit und das Endraupenstadium des Wirts. Zudem wurde der Prozentsatz der Parasiten, die in einem Wirt erfolgreich ihre Entwicklung abschlossen und schlupften, durch die Parasitenzahl bestimmt. Parasitierte Raupen nahmen langsamer an Gewicht zu und erreichten ein geringeres Endgewicht als nichtparasitierte Vergleichsraupen; dies wurde auf geringere Futteraufnahme der parasitierten Raupen zurückgefuhrt. Nach der Parasitierung von Manduca Raupen direkt nach der funften Hautung war die Entwicklungsgeschwindigkeit von Apanteles beschleunigt im Vergleich zu derjenigen in parasitierten Jungraupen. Die Parasitierung verursachte auch Entwicklungsanderungen in Manduca‐Raupen, die Apanteles einkapselten und aus denen keine Parasiten schlupften Unsere Beobachtungen deuten an, dass solche Raupen einen hohen Juveniltiter bis spat in der Raupenentwicklung behalten, was eine normale Metamorphose verhindert.

Cotesia congregata polydnavirus (CcPDV) is essential for successful parasitism of Manduca sexta larvae by the braconid wasp Cotesia congregata. To determine the molecular mechanisms for the vertical transmission of CcPDV in the wasps, we analysed the different forms of the virus sequences containing the gene encoding the early parasitism-specific protein 1 (EP1). By a detailed molecular analysis, we demonstrated that the EP1 sequences are present in wasp DNA in two forms : a circular form as seen in the virus particles and a form integrated into the wasp genome. Moreover, we showed that the integrated form of the EP1 sequences is able to excise in the ovary cells. A fragment corresponding

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The ovaries of endoparasitic species of braconid and ichneumonid wasps contain large numbers of polydnavirus (PDV) virions that replicate in specialized calyx cells of the ovaries and are injected into the host larva during parasitization. In the braconid wasp Cotesia congregata that parasitizes the tobacco hornworm, Manduca sexta, the total amount of viral DNA present in the ovaries was determined to be 25-75 ng. Analysis of viral DNA on 0.4% agarose gels showed that the genome was comprised of 15-20 circles of double-stranded DNA. SDS-PAGE analyses showed that a large number (>30) of structural polypeptides were present in the virions, and analysis of the venom likewise showed that multiple components were present. The major size classes of venom proteins differed from those present in the PDV. However, Western blots using polyclonal PDV antibodies showed that some cross-reacting PDV-like proteins were present in the venom, perhaps explaining the mild PDV-enhancing effect of the venom. Injection of PDV into unparasitized larvae provoked pronounced alterations in their growth, development, pigmentation, and hemolymph proteins. A densely staining band of hemolymph proteins of approximately 18-20 kD appeared in large amounts relative to other hemolymph proteins several days following injection of PDV; this band was undetectable in naturally parasitized larvae. Eggs which had been washed extensively to remove PDVs were encapsulated following injection, but development of the host still was disrupted, usually in the post-wandering prepupal stage. Thus,

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