ABDOMEN. 61 



Tlie abdomen of the insect, to which we next turn our 

 attention, is the third great section of the body, and the 

 seat of the organs of res})iration and generation, and 

 most of those of digestion. It consists of a series of 

 rings usually without any appendages, thougli they ex- 

 ist in some species, as the external organs of generation, 

 or as filiments, &c., attached to the extremity of tlie body. 

 The typical number of these rings is eleven, and they 

 are connected together wilh an elastic tissue, or mem- 

 brane, which permits them to move one upon the other 

 as joints ; this number cannot, however, be counted in 

 all insects for two or three of them are often joined to- 

 gether, or modified, as special organs, as stings, oviposi- 

 tors, &G. 



The abdomen may be observed in i-elation to its s?jylh 

 staiice^ articulation^ with the trunk, composition^ shape 

 clothing^ and appendages, or special organs ; of each of 

 these points we will say a few words. 



I. Substance. — In this connection the observer may 

 notice the degree of hardness, finiiness, or flexibility of 

 the rings of the abdomen. When the body is covered 

 by hard elytra, as among the beetles, the upper part is 

 softer than the under or ventral portion ; but in the 

 open ringed insects the opposite is the case. 



II. Jirticulation xcith the Trunk. — There are two ways 

 in which this is effected : The first, where the entire 

 width of the abdomen is attaclied directly to the trunk; 

 and the second, where the abdomen and trunk are con- 

 nected by a more constricted, and often a very slender 

 and even thread-like waist ; such is the case with many 

 of the ichneumen iiies. 



