168 BRITISH TYROGLYPHID^. 



serve as supports to organs of suction; he also de- 

 scribes mandibles and a lingua, but then he describes 

 genital organs and the mode of coition ; in which, of 

 course, he was mistaken ; as the creatures are immature. 

 His paper is beautifully illustrated. 



This part of the present chapter may properly con- 

 clude by an account of the rudimentary, probably 

 rather expiring than nascent, condition of the hypopial 

 stage in some of the common species of Glycyphagus. 

 This is not one of the genera in which functional 

 Hypopi usually occur ; in some of those species which 

 are associated with mammals the homopial Hypopi 

 occur ; indeed, they are confined to this genus, but 

 they are only found in that small section of it for 

 which Haller sought to create the genus Dermacarus. 

 These Hypopi are active creatures, and the stage is 

 thoroughly functional, but no active hypopial nymph 

 is known in any of the other species, nor was any 

 rudimentary hypopial stage known amongst them 

 until the investigations by Megnin * and by my self, t 

 which will now be related. 



I have before given an account of the inert stage 

 which precedes each ecdysis. In May, 1885, when 

 examining some material swarming with Glycyphagus 

 domesticus in various stages, I observed that there 

 were some that could only be classed as inert nymphs, 

 but had not quite the ordinary appearance of the 

 creature in that stage : the cuticle was more opaque, 

 and seemed thicker and whiter, the back was more 

 arched, the empty skin of the legs was more apt to be 

 rubbed off, as if the inert stage had lasted longer than 

 usual, giving a case-like appearance ; I speak of them 

 as " cases ; " each " case " is only a nymphal skin, but 

 it is a skin under special conditions : one is drawn (PL 

 VIII, fig. 12). The fine marking of the cuticle was 

 resolved under a highish amplification into the labyrin- 



domesticus and 

 G. 



