STRAY NOTES ON CERTAIN SPECIES OF BUTTERFLIES. 193 



On the impal icing in Butterflies. — In the Trans. Linn. Soc, Ser. 2, 

 Zool., vol. v., pp. 255-257, is a paper by Prof. Poulton on " The form of 

 the imaginal fore wing detected on that of the pupa," in which he 

 deduces certain conchisions based on the assumption that " ahhough 

 the wing of the imago expands into a size far beyond that reached by 

 tlie pupal organ Avithin which it is developed, the former does not en- 

 tirely till the latter before emergence," and that " the margin of the 

 imaginal wing lies well within the corresi^onding margin of the pupal 

 wing." As I have been paying considerable careful attention to points 

 of structure in our butterflies this year, I found some peculiarities in the 

 structure of the wings of certain species, which could hardly be explained 

 by Prof. Poulton's theory. These pupje and suggestions I submitted 

 to Dr. Chairman, and he informed me that he had already come to the 

 conclusion that Prof. Poulton Avas wrong, and made several suggestions 

 relative to the matter. As there is no time like the present, and I had 

 a considerable amount of material coming to hand, I commenced to work 

 on Dr. Chapman's suggestions, and set myself to test Mr. Poulton's 

 assumptions, with a view of considering whether the conclusions could 

 be justified. I found, as Prof. Poulton remarked, that " the two margins 

 (pupal, and so-called imaginal) are often separated by an interval, but 

 their contours are frecpiently very different," and I made out as I thought, 

 tliat " in many species the position of the future margin of the imaginal 

 wing can be distinctly made out on the pujial surface from the very be- 

 ginning of the pupal period, and, long before the imaginal organs have 

 begun to api^ear." The line which appears to correspond to the future 

 imaginal hind margin is " especially distinct, and is separated from the 

 hind margin of the j)upal wing, by a very wide interval." Having 

 made, on a large number of pupa?, the superficial observations necessary 

 to test the assumed facts mentioned above, and on which Prof. Poulton's 

 paper is based, I found that a number of species such as the pupa of 

 Lasiommata cegeria, three species of Argynnis, and the Avhole of the 

 Vanessas (except antiopa), had within the margin of the pupal wing, a 

 more or less distinct line, bearing a more or less resemblance to the 

 contour of the imaginal wing, and which I had no difticulty in deter- 

 mining to be the supposed outer margin of the imaginal wing. I was 

 not altogether satisfied, however, that tins line had anything like the 

 positive relationship to the actual imaginal Aving Avhich he gaA-e it, nor 

 did I get anything like so positiA^e an idea that this Avas the limit of 

 " that part of the pupal fore Aving, beneath Avhich, the imaginal wing 

 Avill develop," although "the lines Avhich correspond to the future A'ena- 

 tion " Avere certainly " more or less visible in this area." Dissection 

 shoAved clearl}^, that some structure was in this area betAveen the tAvo 

 assumed margins, and as the hind Aving projected but A-ery little in most 

 instances Ijeyond the pupal fore Aving, I felt that the structure had 

 something to do Avith the imaginal fore Avang. I was further stimulated 

 by supposing that this portion of the Aving might represent the thick- 

 ness of the imaginal Aving, and so I kept close obserA^ation on the pupte, 

 during the time that the imaginal Aving Avas in process of formation. 

 The first species to Avhich I gaA^e this special attention Avas Lasiommata 

 ti^geria. The imaginal Avings three days before emergence Avere of a pale 

 Avhitish-broAvn colour, extending beyond the so-called imaginal hiv>d. 

 margin to the pupal hind margin. Next day, the broAvn colour shoAved 

 that this observation Avas correct, Avhilst on the morning of emergence, 



