222 THE HYMENOPTERA. 



neck, which gives it great power of motion. The 

 eyes, which are placed on the sides of the head, are 

 generally large, and in the males of many species 

 they occupy nearly the whole upper surface of that 

 part of the body, leaving only a space in front for the 

 insertion of the antennee and of the ocelli, which are 

 almost always present, and three in number. The 

 antennae are very variable in length and form, being 

 sometimes short and stout, or even clavate, sometimes 

 pectinated, and sometimes long, slender, and tapering. 



The whole body is always enclosed in a hard skin, 

 which is especially firm upon the thorax, the anterior 

 segment of which (the prothorax) is very small, but 

 distinctly separated from the others, whilst the meso- 

 and metathorax are fused into a somewhat oval mass. 

 The six legs articulated to the thoracic segments vary 

 considerably in form in particular groups, but they 

 are generally long and slender, and terminated by 

 five-jointed tarsi. 



The abdomen is composed of a variable number of 

 horny rings, which is even sometimes different in the 

 two sexes of the same species; it is sometimes at- 

 tached to the metathorax by the whole breadth of its 

 base, whilst in the majority, the basal, and frequently 

 also some of the following segments, are greatly nar- 

 rowed, so as to form a thin stalk ; and so slender is 

 this in many cases, that we can scarcely imagine how 

 the mass of the abdomen is supported in its proper 

 position by such a mere thread. Throughout the 

 order, however, the abdomen of the female is termi- 

 nated by a valvular sting or ovipositor, and the essen- 

 tial nature of this organ appears to be the same in 

 all the species, although its structure is modified to 

 suit their various necessities; and in certain groups 



