574 EXTERNAL ANATOMY OF INSECTS. 



12. Pleura a . By this name I would distinguish the 

 part which laterally connects the metathorax and post- 

 pectus. It includes in it the socket of the secondary 

 wings. In the Coleoptera this is a two-sided piece lying 

 between the postfrcenum and the parapleural with the 

 upper side horizontal and the lower vertical b — a tendon 

 usually proceeds from its anterior extremity to the base of 

 the wing. In the Orthoptera, Neuroptera, and other Orders, 

 it is merely the longitudinal line of attachment of that 

 part ; but in the genus Belostoma Latreille, related to the 

 water- scorpion, it presents a peculiar structure, being a 

 deep channel or demitube, filled at its posterior extremi- 

 ty by a spiracle and its appendages c . 



1 3. Metapnystega d . This part, although in the table I 

 have placed it as an appendage of the pleura, is not always 

 confined to them, as you will soon see. It either covers 

 aerial vesicles, or is the seat of a spiracle. In the Order 

 Coleoptera it is of the former description. If you exa- 

 mine the metathorax of the. common dung-chafer (Geo- 

 trupes stercorarius), in the horizontal part of the pleura 

 you will see a sublanceolate or subelliptical rather mem- 

 branous silky tense plate, with its point towards the. head, 

 — this is the part we are considering ; something similar 

 you will find in most beetles; but in some, as Callichroma 

 moschatum, it is less conspicuous. This part, as far as I 

 have observed, is not so situated in any other Order, ex- 

 cept in some Heteropterous Hemiptera: in Belostoma the 

 channel lately mentioned is filled up at its posterior end 

 by a red organ with an anterior vertical fissure, termi- 



a Plate VIII. Fig. 3. w. » Plate XXII. Fig. 14. w' . 



e Plate XXIX. Fig. 25, w\ 



d Ibid, and Plate VIII. Fig. 12.; and Plate IX. Fig. 7. k" . 



