THE ABDOMEN, 13 
The abdomen consists of six segments, in the queens 
aud workers, that is to say in the females, and seven in 
the males. The first segment, as a general rule, in the 
Formicide forms a sort of peduncle (known as the scale 
or knot) between the metathorax and the remainder of 
the abdomen. In the Myrmicidz two segments are 
thus detached from the rest. 
The Poneride form, as regards the peduncle, and 
in some other respects, an intermediate group between 
the Formicide and the Myrmicide. The second abdo- 
minal segment is contracted posteriorly, but not so 
much so as to form a distinct knot. 
The form of the knot offers in many cases valuable 
specific characters. 
I have sometimes been tempted to correlate the 
existence of a second knot among the Myrmicide with 
their power of stinging, which is wanting in the For- 
micide. Though the principal mobility of the abdomen 
is given in the former, as in the latter, by the joint 
between the metathorax and the knot, still the second 
segment of the peduncle must increase the flexibility, 
which would seem to be a special advantage to those 
species which have a sting. It must indeed be 
admitted that Ccophylla! has a sting, and yet only 
one knot; but this, of course, does not altogether 
negative my suggestion, which, however, I only throw 
out for consideration. 
' Proc. Linn. Soc., vol. v. p. 101. 
