on various Species of Hymenopterous Insects. 131 
to stand obliquely with respect to the right line, and their point of 
course projects a little beyond the plane of the blade, without 
being laterally bent. And all those in each blade thus project a 
little outwards, but the kerf is more effectually made, and a free 
range procured for the saws by small teeth, placed on the outer 
side of each; so that, while their vertical effect is that of a saw, 
their lateral effect is that of a rasp. In the artificial saw the teeth 
all point outward (towards the end) and are simple; but in the 
saw of the Tenthredo they point inward or toward the handle, and 
their outer edge is beset with smaller teeth, which point outwards 
(towards the end).” Valisnieri, Reaumur, and De Geer describe 
the groove as being in the back; but in Mr, Peck’s insect, if there 
is no error in his account, it is, as in the Cicada, in the saw itself. 
In the genus Cimbex, belonging to the same tribe, the saw differs 
in shape, being somewhat sigmoidal, or resembling the letter S, 
while in that of other saw-flies it is cultriform, with a concave edge : 
other minor differences distinguish them, which need not be par- 
ticularized. 
In Cephus the valves and the ovipositor itself are formed as in 
the Tenthredinide, except that the sheaths and the saws are not 
transversely striated ; the connexion between each sheath and saw 
having the appearance of a longitudinal stria, and, in fact, begin- 
ning to assume somewhat of the horny appearance of the ovipositor 
of Urocerus, between which and the ovipositor of Xiphydria I 
cannot perceive the slightest difference of structure. 
The last segment of the abdomen of the female of Urocerus 
juvencus appears, when viewed on the under side, as though 
divided into two segments, the apical part having at its base an 
excavated spot, which Latreille* regards as the anus. 
Notwithstanding, however, the differences which certainly exist 
in the formation of the organs inclosed in the bipartite scabbard 
and valves in the different families above referred to, I think, from 
the circumstance of the minute styliform processes and the two 
external valves being similarly constructed in all these groups, we 
may without much difficulty trace the analogies of the other parts, 
(as has been attempted in detail in the 2d volume of my “ Intro- 
duction to the Modern Classification of Insects.’’) 
The manner in which the eggs are deposited by the ovipositor of 
the Uroceride and Ichneumonide does not appear to be ascertained, 
or whether the horny sides of the terebra are capable of extension 
on their under side. Messrs. Kirby and Spence observe upon the 
* Genera Crust. vol. iii. p. 238. 
K 2 
