382 SYSTEM OF INSECTS. 
6. Hymenoptera 3 [Piezata F.). Mr. MacLeay con- 
siders Sirex L. as being osculant between the Order we 
are now entering upon and the Trichoptei'a, and Ten- 
thredo, L. as belonging to the latter. He appears to 
ground this opinion chiefly upon a consideration of their 
larvae and a slight difference in their ovipositor. As the 
Order, as settled by Linne, has always been deemed one 
of the most natural ones, and all the great Entomolo- 
gists of the present sera have agreed with him in thinking 
it so ; it seems to me that to prove them mistaken in this 
opinion, the question should have been discussed at more 
length, and that it requires arguments of more weight 
than any Mr. MacLeay has at present produced to set it 
aside. He appears in general to lay great stress upon 
an agreement in larvae and the kind of metamorphosis ; 
and I am ready to acknowledge that it forms a strong 
presumption in favour of any hypothesis of affinity be- 
tween certain tribes. But when it is had recourse to as 
fundamcntatjvtind infallible, I think it is pushed far be- 
yond what it will bear, or is warrantable. I may be 
wrong ; but in my apprehension, a striking agreement 
in their general structure in the perfect state, which is 
the acme of their nature, affords a much more satisfac- 
tory reason for keeping two tribes together, than any 
difference observable in their larvae or metamorphosis, 
for separating them. Let any one compare the structure 
of these two tribes with the Trichoplcra 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 J urine's plates 
of the wings of Hymenoptera is calculated to produce 
:1 From vuvi'j, a membrane. 
