ANATOMY AND PHYSIOLOGY. 109 
- The membrane of the wings which is spread out 
on this frame-work is twofold, the nervures lying 
between the two layers, like the sticks in a paper fan. 
The outer surface is set with small short hairs or 
bristles which are most largely developed on the 
front edges of the wings. On the front edge of the 
hind pair, these hairs are for a short space still more 
enlarged, and turned over so as to form a row of 
spiral hooks. These hooks vary much both in form 
and number in the different orders of Hymenopterous 
insects. In all the female Vespz which I have exa- 
mined, both English and foreign, there were thirty- 
two hooklets. Butin the males, both of the hornet and 
of the smaller species of English wasps, the number 
was considerably smaller and very uncertain. One 
had thirty, one twenty-eight, one only fifteen, but the 
greater part had from eighteen to twenty hooks. In 
one Odynerus there were fourteen only, while in dif 
ferent species of sand-wasps from Penang they ranged 
from nineteen to fifty-seven. Mr. Newport* infers, 
from the occurrence of a smaller number of hooklets 
in the weaker flying of the two sexes, that their 
number has a direct relation to the power of flight. 
Thus, the feebly flymg male of the humble bee has 
only eighteen, while his partner has twenty-five ; and, 
conversely, the male of the honey-bee, which flies so 
strongly, has twenty-one, while the female and worker 
have only seventeen and nineteen respectively. I 
would not question the general inference, but I doubt 
whether the numbers are constant enough to build 
any accurate conclusion upon. The numbers in the 
female Vespz have appeared to me constant. But I 
* ‘ Cyclopeedia Anat. Phys. Insecta,’ Vol. II, p. 980. 
