A CYTOPLASMIC POLYHEDROSIS OF HEMEROCAMPA PSEUDOTSUGATA

Histochemical and histological studies of midguts of larvae of the Douglas-fir tussock moth, Hemerocampa pseudotsugata, infected with cytoplasmic-polyhedrosis virus showed that the viral inclusion bodies formed in apicobasally oriented rows in goblet and columnar cells of the epithelium. Electron micrographs of ultrathin sections of infected cells in the late stages of the disease revealed that the cytoplasmic polyhedra, were surrounded by high numbers of virus particles, adjacent to the surface of the inclusion bodies. Biological assay gave an ld50 estimate of 104 polyhedra/g larval weight. In our samples, the mean volume of the inclusion bodies was 7.7 μ3 and the mean diameter of the virus particles was 56 mμ. © 1969.