抄録
Besides typical red-headed and black-headed types of Hyphantria cunea, another type which is characterized by the larval heards 'mosaic' of red and black, were found in Pacific areas of North America. Collection of the larval specimens or the larval heads in abandoned nest-webs showed that, despite the variation in color of the larval heads from blackish to uniformly red, the behavior of larvae (noctornalism, hiding under the nest-web till the last instar, etc.) is identical with that of the red-headed type. The type reported here could be considered as a northern strain of the typical red-headed type and thus the two were joined under the name of Malacosoma type, resulting that there are two biologically distinct entities in the fall webworms, that is the black-headed type (H. cunea) and the Malacosoma type webworm. It was also suggested that the examination of wing-maculation of the overwintered male moths over North America is needed before the determination of the specific status of the latter.
