Introduction. Entomopoxviruses (EPVs) were first discovered by Vago (1963) and subsequent research has shown that they bear close morphological resemblance to orthopoxviruses except they are distinguished by being occluded in a proteinaceous matrix at the end of the viral replication cycle. The occlusion body (OB), which has been called the spheroid because of its shape, stabilizes the virions within and provides a certain amount of protection against inactivating agents in nature such as UV light and heat (Fig. 1). The spheroid of many EPVs, such as those from Choristoneura biennis (CbEPV), C. fumiferna (CfEPV) and Heliothis armigera (HaEPV), contains the virions and another spindle-like structure which seems to be composed of a single protein called fusolin (Dall et al., 1993). These authors called it fusolin in recognition of Professor C. Vago (‘fuseau’ meaning spindle in French).