110 HYMENOPTERA. 



mining operations, and are worked like trowels to collect moist 

 clay, and to apply it to the masonry of their habitations." 

 (Shuckard.) 



The four wings are present, except in rare instances. They 

 are small ; the hinder pair long, narrow, ovate, lanceolate. 

 The costal edge of the fore-wing (Fig. 29), is generally 

 straight, becoming a little curved towards the apex, which 

 is obtusely subrectangular ; the outer edge is bent at right 

 angles, while the inner edge of the wing is long and straight. 

 The veins are often difficult to trace, as in the outer half of the 

 wing they break up into a system of net-veins, which are few 

 in number, yet the continuations of the subcostal, median, and 

 submedian veins can be distinguished after careful study. 



In some low Ichneumonidce, the Proctotrupidce, and 

 Chalcididce, the veins show a tendency to become obsolete, 

 only the simple subcostal vein remaining ; and in Pteratomus, 

 the veins are entirely obliterated, and the linear feather-like 

 wings are in one pair fissured, reminding us of the Plume- 

 moths, Pterophorus. 



The abdomen is composed in the larva state of ten segments, 

 but in the adult stinging Hymenoptera, of six complete seg- 

 ments in the females, and seven in the males ; while in the 

 lower families the number varies, having in the Tenthredi- 

 nidoe, eight tergites on the upper side and six sternites on the 

 lower side. The remaining segments are, during the transfor- 

 mations of the insect, aborted and withdrawn within the body. 

 The ovipositor and corresponding parts in the male have 

 been described on pp. 14-18. 



The nervous system consists in the larvse of eleven ganglia, 

 in the adult, five or six of these remain as abdominal ganglia, 

 while the remainder, excluding the cephalic ganglia, are placed 

 in two groups in the thorax. The cerebral ganglia are well 

 developed, evincing the high intellectual qualities necessary in 

 presiding over organs with such different uses as the simple 

 and compound eyes, the antennae, and lingua and palpi, and 

 mandibles, especially in those sociable species which build 

 complete nests. 



The digestive system, in those bees which sip up their food, 

 consists, besides the external mouth-parts, of a " long oesoph- 



