374 SYSTEM OF INSECTS. 
the acme of their nature, affords a much more satisfac- 
tory reason for keeping two tribes together, than any 
difference observable in their larvee or metamorphosis, 
for separating them. Let any one compare the structure 
of these two tribes with the Trichoptera on one side, and 
the Hymenoptera on the other, and it will require but 
a glance to convince him of their greater affinity to the 
latter ; and the simple inspection only of Jurine’s plates 
of the wings of Hymenoptera is calculated to produce 
the same effect. With regard to their larve, the re- 
semblance between the case-worms and the pseudo-ca- 
terpillars of the saw-flies seems to me very distant, and 
the numerous prolegs of the latter have scarcely a legi- 
timate representative in the former. The larve of the 
genus Lyda F. (Cephaleia Jur.) lose the prolegs intirely, 
and in one species, which much resembles the vermiform 
larvee of Hymenoptera, the real legs are so extremely 
short as to be scarcely discernible*; so that it requires 
no great stretch of faith to believe that saw-flies or S7- 
rices may exist in which the legs disappear>. But it is 
this very tribe, whose larvee thus approach to those of 
the other Hymenoptera, in which Mr. MacLeay finds 
the greatest external resemblance to the Trichoptera‘. 
In fact the difference between the saw-flies and Szricide, 
and the remainder of the Hymenoptera, amounts to little 
more than what takes place in the Diptera Order be- 
* De Geer ii. 1035. " Since this was written, 
Mr. Stephens has showed me a remarkable Hymenopterous insect 
taken by him in Hertfordshire, which appears to have the antenne 
of one of the Ichneumonide and the wings and abdomen of a Ten- 
thredo L., so as to form alink connecting the two tribes or suborders. 
This may probably have a vermiform larva. 
© Hor, Entomolog. 431. 
