ENTOMOLOGICAL SOCIETY OF ONTARIO. 65 



requires the action of the fluid to expand the wing, the natural inference is, that similar 

 causes are required to produce similar results in the scale ; but whether there is an open- 

 ing in the scale corresponding to that at the base oE the wing, to admit the fluid, or 

 whether it enters by cell absorption, has yet to be demonstrated. In the great majority 

 of cases the scales have their colors decided in the chrysalis, by internal pigments pro- 

 bably. What change takes place, if any, during expansion, I have not been able to ascer- 

 tain, except a perceptible brightening of the colors. 



After my paper was written I received from Mr. Balk will a chrysalid of I), archippus, 

 which had matured up to the point of emerging, then died before accomplishing it. I 

 removed a winglet and proceeded to investigate. I failed to extend this winglet as com- 

 pletely as I did that of Polyphemus. It was much more elastic, and I could draw it out 

 about half its own length, but it would go back again, and it was easier drawn out 

 laterally than longitudinally. I found it impossible to remove the scales by any means 

 at my disposal, and was becoming hopeless of seeing the structure of the membrane. I 

 removed the costal nervure, and when exj,mining the cut edge with a lens I perceived in 

 one place that the edges of the membranes had parted. By many efforts and steady direct- 

 ing I succeeded in getting the point of a pin between them, when I found that the wing- 

 let was like an empty sac. The two membranes were not in the least attached ; even at 

 the edges there was no pressure required to separate them, and the only thing that showed 

 any symptom of holding them together was the fringes ; so I separated the two mem- 

 branes clean from base to apex without an effort, when the whole structure of the winglet 

 was exposed to view. The nervures are in the upper membrane, with a groove in the 

 lowei', opposite, into which they fit. Both membranes are structurally alike, but the 

 gatherings are perceptibly finer in the lower as compared with the upper. The surface, 

 under the microscope, presented the appearance of a multitude of light grey transverse 

 lines"with dark spaces between. The gray lines are the under edge of the gatherings, 

 whilst the dark spaces are the openings into the loops, on the crest of which the scales 

 are situated. The transverse lines are not solid lines, but seemed to be made up of minute 

 elongated dots. Near the base of the winglet some of the lines had the appearance of 

 being composed of wide-spread Ws. Elsewhere the lines of the W's were erect and closely 

 packed. This gives quite a different view of the wing structure from that obtained in my 

 former observations of the upper surface of the membrane. Here we see all the material 

 that is required for producing a wing two inches in length by one inch at its widest part, 

 compressed into a space less than three-fourths of an inch long and three-eighths wide. We 

 also see that ther^ is nothing to prevent its rapid, or even instantaneous expansion when 

 the fluid from the living insect enters between the membranes in sufficient quantity and 

 force ; but that is required for the purpose, and nothing else seems capable of producing 

 the wing extension ; but why the fluid does not escape at the edges I do not know, and 

 yet all the butterflies that I have observed burst their chrysalis always let fall some drops 

 of fluid, and it may be that this is whence they come, and which would also account for 

 the general external moistness of the imago at that time. 



But to return to a consideration of the moths. I am now convinced that there must 

 be an actual growth of the lower membrane during the progress of their wing expansion. 

 There is nothing in its structure resembling the gatherings observed in the lower mem- 

 brane of this butterfly. There is an appearance of looseness in its texture, but it has none 

 of the elasticity of the other ; it would tear rather then yield. Then again, when small 

 moths are expanding their wings, the edges invariably curl under, as if the upper surface 

 was extending more rapidly than the lower, which no doubt is the case, and is the cause 

 of the curling, and as they press the two upper surfaces together it assists in extending 

 the lower membrane and straightens out the curls. Here the question arises, are the 

 wings of all moths constructed on the same principle? And are those of butterflies all 

 constructed upon the other ? The further one travels along such a road the greater appears 

 the distance to the end. 

 5 (en.I 



