ENTOMOLOGICAL SOCIETY OF ONTARIO. 63 



REMARKS ON THE STRUCTURE OF THE UNDEVELOPED WINGS OF 



THE SATURNIIDyE. 



By J. Alston Moffat. 



I have had an opportunity of making further microscopical examination into the 

 condition of the undeveloped wings of one of the large Saturniid;e. 



During the winter of 1893 and 1894, I secured a large number of the cocoons of 

 Attacus promethea and Telea pohjphemiis. In the early spring of 1894- I watched them 

 closely, so as to secure, if possible, some of the moths on their escape from the cocoon, 

 before expansion had commenced. 



I was fortunate on being present at the moment of emergence of a fine large speci- 

 men of T. polyphemus, which I killed at once before growth had started. After removing 

 the front winglet from its socket in the thorax, I found that the crimpling of the heavy 

 nervures on the costal margin had relaxed, yet, even with that addition to its size, it 

 measured only five-eighths of an inch in length and about three-eighths at its widest part ; 

 which might have expanded to three and a half inches in length, and one and a half at its 

 widest part. 



I did not discover anything new about the structui-e of the nervures, but I paid 

 especial attention to them in relation to some suggestions that wore made in connection 

 with my former observations, to see how far they might be correct or otherwise. 



One was, that the nervures might be constructed spirally, and that the extension of 

 the membrane of the wing might be produced by, as it were, the relaxing of a compressed 

 spring. I could see nothing to confirm such a view. The prominent rings of each 

 segment made a complete circle. The extension of the nervure is in a straight line, 

 something after the manner of the drawing out of a telescope, only, the one section not 

 merely draws out of the other, but the small end of the one section draws out with it the 

 inside of the large end, and keeps on extending until the nervure is all brought to a uni- 

 form thickness, with a slight reduction to the outer end. 



It has been claimed by some, that the iluid enters the nervures and assists in the 

 extension of the membrane. This, I am satisfied, is not the case. I examined the large 

 nervures of an expanded wing, and found some parts of them hollow, and quite empty, 

 which would not have been so if fluid had entered them. Moreover, the parts of the 

 nervures where the segments unite seem to be solid, somewhat resembling the joints of a 

 bamboo-cane, which would make the passing of the fluid through them almost, if not 

 quite, impossible. My impression is, that the nervures do not in any measure contribute 

 toward the extension of the wing, but depend for their own extension upon the pressure 

 derived from the fluid flowing between the membranes. 



The amount of fluid stored up in a newly emerged imago to be used in expanding the 

 wing, must be very great. One of xnj A. cecropia in coming out of the cocoon, had in 

 some way got a piece torn oflf a front winglet. Whilst expanding, fluid began to show at 

 the break, and by the time the wing was fully extended, large drops hung all along the 

 broken edge. This wing expanded as perfectly as the unbroken one ; showing that there 

 was enough fluid to do the work and some to spare. 



I thought by maceration and manipulation to draw out the winglet to some extent ; 

 but was disappointed and not a little surprised to find that I could make little or no 

 impression upon it in that direction. I afterwards thought thnt T discovered the reason 

 of my failure. 



I succeeded in cutting out a longitudinal section from between the heavy costal 

 nervures of the winglet. Placing it on one of its cut edges under the microscope, I found 

 that I had got a beautiful and intensely interesting object of contemplation. The gather- 

 ings of the membrane on the upper surface of the winglet, lay before me in a uniformly 

 symmetrical row of elongated loops, with a row of tiny scales on the crest of each. The 

 loops were nearly closed at their base, widest a little above their centre, making a narrow 

 curve at their apex, open and quite empty. I looked for, and expected to find in the 



