Studies on sex chromosomes of the silkworms, Philosamia cynthia ricini and Dictyoploca japonica

X Chromosomes during the prophase of the cell meiosis in the female silkworms of Philosamia cynthia ricini and Dictyoploca japonica were observed. The length, the ordinal number of X chromosome in the whole chromosome complement and the character of heterochromatin region in Dictyoploca japonica^s X chromosome suggested that the XO pattern, to female Philosamia cynthia ricini, was in accord with the second view;while to female Dictyoploca japonica, it might occur in Y chromosome merging into X chromosome.