12 



accustomed to call them, are hollow tubes, convex on the 

 upper surface, flat, and of a slighter texture on their under- 

 side." 



All authorities seemed to agree that the wings were in 

 the shape of a bug which had been flattened. And the 

 question arose in my mind as to whether the two surfaces 

 were quite separate, or whether they were joined along the 

 nervures. Prolonged masceration in potash, I found 

 separated the upper from the under surface, except a sliglit 

 attachment at the margin, and by gently pulling I was able 

 to divide the wing completely in half, and by floating the 

 two halves on a slip was able to mount them. The next 

 question was to decide as to the formation of the nervures. 

 Three solutions presented themselves to me as being likeh- : 

 First, that they were tuburlar, being an attachment of one 

 surface, the other surface being merely a covering ; second, 

 that they were tubular, but on both surfaces superimposed ; 

 third, that they were half tubes on each surface but joined, 

 forming a tube when united together. This latter I found 

 to be the correct solution in certain cases, but so far I have 

 failed to satisfy myself that the open part of the tube is 

 not covered with an exceedingly fine transparent membrane. 

 But in other cases the tube is confined to the under surface, 

 the upper one being merely covered with a slight thickening 

 where it comes in contact with the true nervure. 



There also appears to be two methods of expansion of 

 the wings. I find in Pavonin carpini, the emperor moth, 

 there are valves at irregular intervals, similar to those in our 

 veins, the nervures may be telescoped or introverted, as is 

 so often found in insects. In Scsia boiiihlylcformis, the 

 bee clearwing moth, I found a different construction. No 

 valves are visible, but in place there is a straited tube 

 running inside the hollow nervure, which is evidently elastic 

 and capable of stretching. In either of these structures 

 the weight of a fluid running into the wings would be 

 sufficient to expand them to their full capacity, the super- 

 fluity finding its way into the tubes, where it would congeal. 



