490 



HYMENOPTERA 



CHAP. 



thereto. It exhibits, however, considerable variety, and is seen 



in its simplest and least soldered state in 

 Cephics. 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 Xylocojpa). 

 We have already remarked that in 

 Hymen op tera 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 Yiq. 334. Pronotum of a car- 



bees in ques- p^^*^^ ^^^^' ^y^ompa sp. 



^ East India. 



tion the pro- 

 notum makes up for the removal of the 

 corresponding side -pieces and stern vmi, 

 Fig. 333.-Alitmnk of Sphex "^1 becoming itself a complete ring, 

 chrysis. A, Dorsal aspect : \^^ sidcs being prolonged and meeting 



a, pronotum ;&,/, mesono- . ^, , /^ . , 



turn; c, teguia ; d, base of m the middle luie ot the under sur- 



anterior,e,of posterior, wing; ^^^^ ^f ^^ \)Q^^r^ ^t the Same time 

 </, division of metanotum ; ^, , '' 



median (true first abdomi- a large lobc IS developed laterally on 

 nai) segment ; i, its spir- ^^^ g-^jg overlvins: and protecting the 



acle ; h, second abdominal ' ./ o x ^ o 



segment, usually called the first breathing orificc. The intermediate 

 petiole or first abdominal ^ ^ ^^ remarkable modification 



segment. B, Posterior as- o 



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



ment: a, upper part; 6, ^p^^p^ nf o-PTipra of bpps 

 superior, c, inferior abdomi- SCrieS 01 genera 01 DCes. 



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

 plate of median segment : , t j. t. ^^ -i i 



g 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 Cimhex 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 



