THE THORAX. 67 



The thorax. 



The tliorax consists, as usual, of three segments, pro- 

 thorax, mesothorax and metathorax, each bearing a pair 

 of legs. The prothorax is generally the smallest of the 

 three, and is, indeed, in many genera completely covered 

 by the mesothorax, in consequence of which the meso- 

 thorax has been more than once mistaken for the 

 prothorax ;^ thus, in Lepidocyrtus the projecting seg- 

 ment is the mesothorax, and not the prothorax, as 

 might at first have been supposed. The three pair of 

 legs do not generally differ much from one another in 

 size ; the anterior pair are generally, however, the 

 shortest and weakest, the hinder pair the longest and 

 strongest. They consist of five segments. The legs 

 are always clothed with hairs, and generally have a 

 certain number which are much longer and stronger 

 than the rest. Some of the species also have one or 

 more teneiit hairs near the foot. In Podura aquatica 

 the legs terminate in a strong curved claw ; but the 

 great number of species are biunguiculate, the two 

 claws not being terminal and opposite, but placed one 

 above the other. In Smynthurus and Papirius the 

 feet are peculiarly formed (PI. LV, figs. 4 and 7 ; PL 

 LXVj figs. 1 — 4), and ofier good specific characters. 



The abdomen. 



The abdomen is globular in the Smynthuridce and 

 Papiriidce ; linear in the Poduridce, Lipuridce, and Anou- 

 ridce. It consists of six segments, which, however, 

 are not well marked in the globular species. The 

 anterior segment is attached to the thorax by its whole 

 base. Each segment is composed of two arches, one 

 dorsal and one ventral. Excepting the last or two 

 last, the dorsal arches are subequal in the Anouridce 



^ See, for instance, Latreille, ' Nouv. Ann. cl. Museum,' 183'J, p. 186. 



