212 BRITISH TYROGLYPHIDJJ. 



the fourth. The vulva is placed just posterior to 

 the coxae of the fourth pair of legs like the penis of 

 the male, but in consequence of the longer abdomen of 

 the female the vulva is much the further from the 

 posterior margin ; it is a mere slit, without chitinized 

 labia, and is often difficult to see. The anus, also, is 

 further from the posterior margin than in the male. 

 The chitinous rings or discs are further forward, and 

 further from the median line than in the male. The 

 posterior margin of the abdomen is much less bifid, 

 only a slight central concavity being usually visible. 

 The posterior tubercle does not constitute the postero- 

 lateral angle, and there are one or two more pairs of 

 small spines on or near the posterior margin than in 

 the male ; in other respects the two sexes are similar. 



Hypopus (PL II, figs. 510).- 



Length . . . . . "14 mm. to "20 mm. 



Average length about . . . *19 ,, 



breadth about . . . '13 



length of first pair of legs about '18 ,, 



Colour when first emerged rosy-pink or vinous, 

 darker and browner after a time. Legs the same 

 colour as the body. 



Texture polished. 



Form ovoid; the thicker end of the oval is the 

 anterior ; the posterior is narrowed. The anterior end 

 of the cephalothorax is a blunt and slightly rounded 

 point ; the posterior is still more rounded. The 

 cephalothorax and abdomen are divided by a well- 

 marked line and constriction ; the latter is about three 

 times as long as the former. Notogaster arched. 

 The lip (fig. 7) is long and narrow, and the two 

 characteristic hairs at its distal end are long, reaching 

 as far as the proximal ends of the tarsi of the first 

 pair of legs when outstretched ; there is a small point 

 or spine outside each hair. There are three or four 



