490 



HYMENOPTERA 



CHAP. 



thereto. 



It exhibits, however, considerable variety, and is seen 

 in its simplest and least soldered state in 

 Cephus. In the higher bees the pro- 

 notum takes on a form not seen in any 

 other Insects, being one of the most 

 beautiful sclerites to be found in the 

 class (Fig. 334, pronotum of Xylocopa). 

 We have already remarked that in 

 Hymenoptera the lower portions of the 

 prothoracic segment are detached from 

 the upper, so 

 that the pro- 

 notum is not 

 supported be- 

 neath by a 

 sternum as 



USUal. In the FlG . 334. Pronotum of a car- 

 bees in OUeS- penter bee, Xylocopa sp. 

 East India. 



tion the pro- 



notum makes up for the removal of the 

 corresponding side -pieces and sternum, 

 FIG. 333.-Aiitnmk of Sphex ty becoming itself a complete ring, 

 chrysis. A, Dorsal aspect : ^ s sides being prolonged and meeting 



a, pronotum ; b, mesonotum ; . . 



c.teguia; d, base of anterior, m the middle line ot the under sur- 



e, of posterior, wing ; /, g face Q f the bo dv At the game time 

 divisions of metanotum ; It, -11 



median (true first abdomi- a large lobe is developed laterally on 

 nai) segment ; i its spir- each s id e , overlying and protecting the 



acle ; /, second abdominal ' * r 



segment, usually called the first breathing orifice. The intermediate 

 Sntt'^Postr^ tages of this remarkable modification 

 pect of the median seg- may be observed by dissecting a small 



ment : a, upper part ; b. f /> i 



superior, c, inferior abdomi- Senes f g enera f beeS ' 



nai foramen ; d, ventral Although the prosternum of a Hymen- 



plate of median segment ; . n -i i 



e> coxa- opterous Insect is not usually visible 



owing to its being overwrapped by the 



side-pieces, it is really, as shown in Fig. 335, B, of complicated 

 form. In Cinibex and some other sawflies the side-pieces are not so 

 large as usual, but the prosternum is larger and is exposed. The 

 prothoracic spiracle is rarely visible externally, but its position 

 is remarkably constant, and is usually indicated by a peculiar 

 lobe or angle of the pronotum projecting backwards just below 



