THE ABDOMEN. 13 



The abdomen consists of six segments, in the qiieena 

 and workers, that is to say in the females, and seven in 

 the males. The first segment, as a general rule, in the 

 Formicidse forms a sort of peduncle (known as the scale 

 or knot) between the metathorax and the remainder of 

 the abdomen. In the JNIyrmicidoe two segments' are 

 thus detached from the rest. 



The Poneridse form, as regards the peduncle, and 

 in some other respects, an intermediate group between 

 the Formicidse and the Myrmicidje. 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 Myrmicidse with 

 their power of stinging, which is wanting in the For- 

 micidse. 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 CEcophylla' 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. 



