Induced changes in the pigmentation of the pupœ of the butterfly P ieris napi L., and their inheritance

It has, of course, long been known that the pigmentation of the pupae of the two lepidopterous species,Pieris brassicœ L. and P.rapœ L. (Poulton, 1887), is influenced by the colour of the light to which the larvae from which they are developed are exposed just before pupation. In particular, if the larvae are allowed to pupate in orange light, a heavy percentage of the pupae obtained is of a bright green colour. This coloration, however, simply depends upon the fact that the formation of the various pigments, white and black, in the chitin of the pupal integument is more or less inhibited by orange light. As a consequence, the colour perceived in pupæ so affected is that of the hæmolymph within, and hence the chrysalids appear green. Recently, in addition to confirming these earlier observations, Dürken (1923) and Brecher (1923) have bred from butterflies reared from the treated larvæ and pupæ. The larvæ descended from the orange glass cultures, even when pupating under ordinary light conditions, gave rise to a set of pupæ including many more green individuals than the control lots. Clearly, therefore, the acquired pupal green had been inherited. In view of current biological controversies, such an effect was of primary importance. Repetition and confirmation of the work were highly desirable, and the present work was therefore undertaken.