280 Mr. E. B. Poulton. Essential Nature of the [Apr. 23, 



means the ova are coloured green or yellow, and the pigments are 

 passed down into the next generation. In this way the newly hatched 

 larva is tinged, and the break in protective colouring is thus filled up, 

 which would otherwise occur before the results of the first meal could 

 become manifest. Hence it might be supposed that the pigments 

 would be retained in the case of female pupae laying green eggs, but 

 not necessarily always in the case of males. Nevertheless the pig- 

 ments appear to be retained equally in both sexes, the only partial 

 exceptions (if any exist) being in the case of dimorphic larvae (green 

 and brown) of which the females are more generally green and the 

 males brown, and I do not think that there are any authentic instances 

 of such a division. In Newman's " Moths " it is stated of C. fflpenor 

 " caterpillar green or brown, the males generally brown," but I have 

 never heard of any confirmation of this statement, and furthermore, 

 the existence of a brown female larva would have to be explained. 

 Last autumn the only larva I could obtain of this species was brown, 

 with brown blood in the pupa, and it proved to be a male. It may, 

 however, be considered certain that the females are sometimes brown, 

 for all collectors seem to admit that the brown variety is far com- 

 moner than the green. It would be well to investigate the subject 

 from this point of view. But I have already stated that the derived 

 pigments are present in the brown blood of this species — in fact the 

 characteristic spectrum of green blood was faintly but distinctly 

 recognisable. Thus it is possible that there is sufficient pigment to 

 tinge the ova, if collected in a comparatively small compass. Another 

 possibility is that the pigments may undergo a slight change rendering 

 them colourless, and that they are reconstructed for the ova. Against 

 this hypothesis it must be urged that some of the pigment certainly 

 remains unchanged. With the exception of this unsettled question 

 my observations point uniformly in the same direction. I have 

 examined the blood in the pupae of the following species which lay 

 green eggs : — Smerinthus Ocellatus, Populi, and Tilioe, Sphinx Ligustri. 

 In all cases the blood is green. E. Angularia is also another in- 

 stance, the larva before pupation, the pupa itself, and the eggs being 

 greenish. 



On the other hand, D. Vinula lays large eggs, but they are reddish- 

 brown from a deposit in the chitinous covering, and resemble spots on 

 the leaves — to the upper sides of which they are affixed — and the 

 young larvae are black and are protected in the same way. In this 

 species the blood of the pupa has lost the green colour which it 

 possessed in the larva, becoming brownish-yellow. 



It is easy to extract xanthophyll in alcoholic solution from ova in 

 the bodies of female moths which have been preserved as cabinet 

 specimens for many years. The eggs, when tinged by derived pig- 

 ments, seem to owe most of their colour to xanthophyll, and they are 



