Abstract
Outbreak of the nuclear-polyhedrosis of Hyphantria cunea was observed in the second generation of 1959 and 1965. Two types of polyhedra were observed: one was hexahedron and the other was tetrahedron. The polyhedra were found in the cell nuclei of epidermis, fat body and tracheal matrix. In the early stage of infection, a chromatin mass appeared in the center of the nucleus, where many rod-shaped virus particles (360mμ×30mμ) were observed. In the surrounding nucleoplasm virus bundles consisting 2-14 rods were found. The membrane-covered rods became enclosed within a polyhedron. In the late stage of infection the nucleus was filled with large number of polyhedra. Interference was observed between the hexahedron virus and the tetrahedron virus. The latter was more virulent and multiplied more rapidly. Nuclear-polyhedrosis virus of H. cunea was not pathogenic to Bombyx mori. The inclusion body of the granulosis of H. cunea was 380-520mμ in length and 200-360mμ in width. They contained single rod-shaped virus particle.
