Abstract
An attempt was made to determine if several inducing agents avairable for the silkworm polyhedroses might be also effective to induce polyhedroses of several other lepidoptera, Barathra brassicae, Hyphantria cunea, Antheraea pernyi, Malacosoma neustria testacea and Lymantria dispar. In general, none of the tested stressors (excessive cold, EDTA, Na-EDTA, formalin and hydrogen peroxide etc.) significantly increased the incidence of polyhedroses. The difference between the silkworm, Bombyx mori and these wild insects in the response to these stressors may be attributed either to the lack of the occult virus or to low aptitude in the wild insects.
The cytoplasmic polyhedrosis virus of Bombyx mori was transmittable to Antheraea pernyi. The shapes of polyhedra formed in the mid-gut epithelium of the latter were not uniform and differed from those of silkworm polyhedra used for the inoculation, which were either tetragonal or hexagonal.
In Hyphantria cunea the authors found tetragonal and triangular nuclear polyhedra, which could be considered to be formed by different viruses respectively. When fed a mixture of the two viruses, the insects were all mixedly infected. The feeding of triangular polyhedra followed later by the feeding of tetragonal polyhedra resulted in the formation of only triangular polyhedra in most of the infected larvae, and the remaining insects were mixedly infected. It was suggested that the first invading virus interfered with the second virus in the infection and multiplication. However, in the case of the feeding of tetragonal polyhedra followed later by the feeding of triangular polyhedra the interference of the first invading virus with the second one was scarecely observed. It may be that the tetragonal polyhedron virus was less virulent than the triangular polyhedron virus and interfered in lower degree with the latter virus.
