394 Mr. F. Merrifield and Mr. E. B. Poulton on 



black patches iu the centre of the wing especially distinct 

 and sharp. 



(3) The Light pupaj. (a) Bone-coloured. These also are 

 perfectly transitional into the Liter mediate pupse. In 

 pupae of this degree the pigment is everywhere reduced, 

 )emaining strongest iu tlie black patches in the centre of 

 the wing, which become excessively conspicuous against 

 the pale bone-colo>ired ground. In some of the most 

 extreme cases these patches become much fainter, but a 

 trace of them is probably always to be found. In other 

 parts the pigment spots and patches are much smaller, 

 and are often represented by minute dots : on the eye 

 it is often absent altogether. 



(3) The Li[/ht pupae, {b) Green. Pigment is never 

 highly developed upon the ground-colour of these pupae. 

 With very rare exceptions it does not exceed the amount 

 ])resent on the light hone-coloured pupae (3 a). The green 

 pupae are far more transparent than the hone-coloured, and 

 the palest are even more deficient in pigment than the 

 palest of the hone-coloured forms. The most important 

 difference in marking has already been mentioned, viz. 

 the absence of the black patches in the centre of the wing 

 (the " wing-mark") even when pigment is developed else- 

 where as greatly as in a decidedly dark hone-coloured pupae 

 of the corresponding degree (3 a) — a pupa which would 

 always possess distinct and prominent patches. Occasion- 

 ally, however, faint traces of the marking may be detected, 

 as minute dots, even in the palest green forms, and very 

 rarely it is fully developed. All marked exceptions will 

 be described below. In the centre of the wing the trans- 

 parency is such that a considerable depth into the pupa 

 can be seen, and the large tracheae distinctly made out. 



Before classifying Mr. Merrifield's numerous pupse, I am 

 tempted to suggest what I believe to be the meaning of 

 this strange dimorphism in marking. The possible failure 

 of my hypothesis would not, however, alter the validity 

 of the observations which I have here recorded. Without 

 attaching too great weight to it, I do not hesitate to 

 suggest the hypothesis, thinking it possible that observa- 

 tion and thought may be stimulated by its means. 



I have just alluded to the great transparency of the 

 green pupae (3 h), and have stateil that this is especially 

 marked iu the centre of the wing, viz. in the exact 

 position of the dark mark on the hone-coloured i[>n^se (3 a). 



