94 MODERN CLASSIFICATION OF INSECTS. 

also exists in the Uroceridee and Ichneumonidz. My jigs. 70. 12—19. 
illustrate the structure of the saws of these insects, as exhibited in 
Trichiosoma Lucorum. Jig. 12. represents the abdomen of the 
female of this insect seen laterally, and 13. the same seen ventrally ; 
jig. 14. shows the extremity of the abdomen beneath, with the ter- 
minal segments partially opened, whilst fig. 15. exhibits the same 
parts seen laterally, with the saws themselves partly exposed. In 
these figures the segments are severally numbered, the ventral arcs 
being distinguished by the addition of x, as 7 x; a indicates the mi- 
nute exarticulate style above mentioned ; b represents the basal, and 
b b the apical part of the outer sheaths of the saws; fig. c repre- 
sents the saws themselves, c showing the back piece or support, and 
e the saw piece (as in /ig.16.) ; in /7g.15. the position of the saws in action 
is represented by the dotted part of the figure ; jig.16. represents one of 
the saws of Trichiosoma separately, and much more highly magnified ; 
Jig. 17. exhibits still more highly magnified part of the edge of the 
sawing part, fig. 18. being one of the minute transversely striated teeth 
of the saw, whilst fig. 19. shows part of the inner surface of one of 
the saws of Cimbex, to represent the zig-zag grooves on its surface. 
The form of the saws varies considerably in its minute details in 
different species, and from its admirable construction it cannot be 
doubted that a careful examination of its various modifications might 
furnish ideas for improved mechanical instruments. In some species 
the edge of the saw is very obtusely serrated, but the longer portion 
of each serration is very finely denticulated. In others the serra- 
tions are much more acute, and the denticulations on one side of each 
of considerable length, in others the edge of the saw is furnished with 
minute rounded lobes, whilst in others these marginal lobes some- 
