During the last decade, several entomopoxviruses have been described that resemble vertebrate poxviruses in shape, structure, chemistry, and morphogenesis (Bergoin and Dales 1971). Melolontha and Amsacta poxvirus have been investigated most extensively, and sufficient information is known about other entomopoxviruses to make some general comments.

For the majority of entomopoxviruses, the fat-bodies, and perhaps hemocytes, appear to be the most susceptible target cells. Usually 1 or 2 tissues are affected, but 2 entomopoxviruses, Chironomus luridus and Amsacta, appear to infect their host systemically.

On the basis of virus-particle size and structure (Table 1), there appear to be 3 subgroups in the genus Entomopoxvirus (Bergoin and Dales 1971). One subgroup, which includes the relatively large viruses affecting the Coleoptera, has a characteristic unilaterally concave core. The intermediate-sized viruses affecting the Lepidoptera possess a nonconcave, symmetrical core structure, and comprise a 2nd subgroup. The 3rd subgroup is composed of viruses affecting dipteran species. These are the smallest of the entomopoxviruses and possess a biconcave core. The entomopoxvirus affecting the migratory grasshopper, Melanopus sanguinipes (F.), appears to be similar to the lepidopteran viruses.

The replicative cycle of all entomopoxviruses appears to be similar, with only minor differences. Replication occurs in the cell cytoplasm, although Henry et al. (1969) reported that M. sanguinipes poxvirus might develop in both the nucleus and cytoplasm of adipose cells.

Two types of inclusions are produced by entomopoxviruses: large, ovoid to irregular-shaped VCIs, and smaller spindle-shaped inclusions devoid of virus particles. Spindles are not produced by all entomopoxviruses and have not been recorded for viruses affecting orthopteran and dipteran species.