DlEPV, a symbiotic entomopoxvirus (EPV) in the accessory glands of the parasitic wasp Diachasmimorpha longicaudata, is transmitted to Anastrepha suspensa (Caribfly) larval hosts during oviposition. A 24kDa parasitism-specific protein (PSP24) appears in host hemolymph concomitant with DlEPV infection. Previous studies demonstrated that PSP24 is encoded by host genes. This study tested the hypothesis that DlEPV and other poxviruses induce PSP24 in cyclorraphous dipteran hosts. Using transmission electron microscopy and a DlEPV-specific antibody (Ab) respectively, we detected DlEPV virions and major structural proteins (70-75 kDa) in A. suspensa hemocytes and fat body within 24 hours post- parasitism (hpp). Likewise, a PSP24 Ab detected PSP24 in the same host tissues within 24 hpp. The abundance of the viral proteins and PSP24 increased with time post-parasitism. Other cyclorraphous dipterans such as Musca domestica and Phormia sp. that were injected with purified DlEPV virions or viral membranes (the DlEPV 70 kDa protein is associated with viral membranes) also expressed PSP24. Interestingly, injection with AmEPV (a lepidopteran EPV) and vaccinia (a vertebrate poxvirus) induced PSP24 in some dipterans but baculovirus injection did not. PSP24 has some homology with Drosophila membrane-associated/defense-like proteins and probably plays a role in cyclorraphan humoral response to infection. These results suggest that DlEPV and other poxviruses have similar structural proteins that induce PSP24, a probable defense-related protein common to cyclorraphous dipterans. This study was supported by NSF grant IBN 9986076 and REU supplement to POL.