OF GLTCIPHAGUS DOMESTFCUS AT^D G. SPINIPES. 289 



considerably longer than those of G. spinipes. Thirdly, G. 

 spinipes has an obtusely conical shape anteriorly, and is suddenly 

 contracted between the second and third pair of legs ; G. domes- 

 iicus has this form indicated but very slightly, being nearly as 

 wide posteriorly as in the middle of the body ; the difference can 

 only be well seen in living specimens. Fourthly, the bursa 

 copulatrix of the female projects considerably more in G. domes- 

 iicus (fig. 7) than in G. spinipes (fig. 15). Fifthly, G. domesticus 

 is a trifle the larger, but this cannot be relied upon. Sixthly, 

 the hairs of G. spinipes are more deeply serrated and stronger 

 than those of G. domesticus. Seventhly, the tibiae of the first and 

 second pairs of legs in G. spinipes each bear two large and thick 

 curved, strongly-serrated hairs ; these are much less developed in 

 G. domesticus. Eighthly, the second joints of the third pair of 

 legs in G. spinipes each bear on the outside a peculiar hair or 

 scale (fig. 14), shaped like a husk of corn, and placed with the 

 concavity inward ; its outer surface is thickly clothed with fine 

 hairs or processes : this structure is most developed in the female ; 

 it has not, I think, been mentioned by previous writers ; 

 it is not found in G. domesticus. Ninthly, G. spinipes when 

 placed on its back, or otherwise disturbed, has a rapid struggling 

 or fighting motion with its first and second pairs of legs, a little 

 of which is seen in its ordinary walk ; this style of movement is 

 very characteristic of the species. 



The Tyroglyphidse, like most of the other Acari, have an inert 

 period previous to each ecdysis ; during this time the creature is 

 motionless and apparently dead, except that it does not shrivel 

 up ; it is needless to say that a proper examination will disclose 

 that the development of the creature in its next stage is pro- 

 gressing inside tlie dead cuticle. 



Glyciphagus domesticus. 



During the month of May, 1885, when I was examining some 

 material wliich had been sent to me and which was swarming 

 with G. domesticus in various stages, I observed that there were 

 some which could only he classed as inert nymphs, but which 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; and I propose in this paper 



