SYSTEM OF INSECTS. 383 
the same effect. With regard to their larva?) 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 
legitimate representative in the former. The larvae of 
the genus Lyda lose the prolegs intirely, and in one 
species, which much resembles the vermiform larvae of 
Hymenoptcra, the real legs are so extremely short as to 
be scarcely discernible a ; so that it requires no great 
stretch of faith to believe that saw-flies or Sirices may 
exist in whose larvae the legs disappear b . But it is this 
very tribe, whose larvae thus approach to those of the 
other Hymenoplera, in which Mr. MacLeay finds the 
greatest external resemblance to the Trichoptcra c . In 
fact the difference between the saw-flies and Siricida?, 
and the remainder of the Hymenoptcra, amounts to little 
more than what takes place in the Diptera Order be- 
tween the Tipulidce, Asilida:, Mtiscida?, &c, in which 
also the metamorphosis differs. 
Another argument upon which Mr. MacLeay seems 
to lay some stress, is taken from the number of parts 
into which the ovipositor of the saw-flies is resolvable, 
which he finds to consist of four pieces ; while in what he 
considers as the genuine Hymenoytera^ it is formed only 
of three d : but in fact, in these last there are two spiculae, 
answering to the two saws of Tenthredo, so that the va- 
a De Geer ii. 1035. b Since this was written, 
Mr. Stephens has showed mc a remarkable Ilymenopterous insect 
taken by him in Hertfordshire, which appears to have the antennaj 
of one of the Ichncumonidcc and the wings and abdomen of a Ten- 
thrcdo L., so as to form a link connecting the two tribes or suborders. 
This may probably have a vermiform larva. 
c Hor. Entomolog. 431. d Hor. Entomolog. 429. 
