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Polymorphisms were readily detected in polydnavirus DNA extracted from several different species belonging to two different families of parasitic hymenoptera. Heterogeneity was observed as differences in electrophoretic profiles of genome segments, differences in the number of cross-hybridizing genome segments, and restriction fragment length polymorphisms; polymorphism was also detected at the level of an individual genome segment. Some implications drawn from these observations are discussed. Key words: polydnavirus, multipartite genomes, DNA polymorphisms.

.. . .. , . .~ .. . . . . . . ... ~ . ' tween the ovarioles and oviduct (N~~-~~~ rt present a matter for speculation, although it might 1975). particle morphogenesis occurs in associa- reasonably be expected that some interaction with . . tion with an amorphous fibrogranular of basement membranes and (or) host cells should the sort commonly observed in vil-ogenic or occur. We considered therefore that as a first step it virus Lf2,ctories.3 M~~~~-~ extracellu12,r pal-ticles would be useful to determine by means of electron consist ofa biconvex nucleocapsid surrounded by microscopy the in uiuo distribution of particles intwo unit memblanes; the inner membrane is as- jected into host caterpillars by female wasps. We sembled de t70v(., and [he is acquil.ed by bud- describe here morphological aspects of early inding into the lumen of the calyx (N~~~~~ et teractions between calyx particles and caterpillar 3975), which often becomes completely filled with particles: viz., the calyx 'fluid.' Calyx fluid parti

A virus was found in the ovarial calyx tissue of Mesoleius tenthredinis, an ichneumonid parasitoid; the "infection" was present in all females thus far examined. Virions were morphologically similar to typical baculoviruses. Apparent uncoating of viral nucleocapsids at nuclear pores was observed, indicating that reinfection of the calyx epithelium may occur. Electron microscopy of DNA extracted from calyx tissue suggests that the viral genome may be circular, and of high molecular weight.

Nuclear inclusion bodies are found in the hemocytes of all tussock moth larvae parasitized by the braconid wasp Apanteles melanoscelus. These inclusion bodies represent the apparent site of replication of an unusual virus-like particle. Identical particles are observed in the nuclei of a small number of parasitoid calyx cells and are probably transmitted to host larvae during oviposition.

Virus-like particles have been found in the female reproductive tracts of all Apanteles spp. thus far examined. Particles generally consist of putative baculovirus-like nucleocapsids which are enveloped singly or as groups within nuclei of calyx epithelial cells. Enveloped particles are injected into host caterpillars during oviposition. Subsequently, particle nucleocapsids appear in the cytoplasm of many host cells, and appear to be uncoated at nuclear pores.

Virus-like particles have been found in specific regions of the reproductive tracts of three different braconid wasps, all parasitoids of the tobacco budworm, Heliothis virescens. The particles are nuclear in origin, and Feulgen cytochemistry of particulate fluid in the calyx and oviducts of one species has revealed the presence of DNA. On the basis of apparent structural homologies, it is suggested that the parasitoid particles are related to baculoviruses.