286 



ARACHNOIDEA. 



CASE shown in Messrs. Fumouze and Robin's memoir on the subject 



XIV. 



in the "Journal de I'Anatomie et Physiologie, 1867." 



The true position of this genus has been the subject of dis- 

 cussion. Latreille, while placing it in the Gamasidae, felt inclined' 

 to approach it to the Sarcoptid^e ; Gervais could not follow him. 

 Koch places it at the end of the Bdellidse ; but it is only in its 

 general predacious structure that it resembles them. The 

 Bdellid^ have long and slender palpi, with five joints ; this has- 

 them strong and thick with three joints, as in the Sarcoptidse, 

 and it is to be noted that the genus Myobia has a tracheal 

 respiratory apparatus not unlike that of Cheyletus. To our mind, 

 it has more affinity with the Acaridae (including Tyroglyphidae and 

 Sarcoptidse) than with any other group. It has the surface strias; 

 of the latter; but it has not their suckers, and it has got the 

 facies of Glyciphagus or Tyroglyphus and some of their cha- 

 racters. On the whole we think it will be best to regard it as a 

 transitional type between the two. 



No. 23. ^ _^ ^ Cheyletus eruditus {Lair., Hist. Nat, 



d. Crust, et d. Insect.), (Ch. casalis,, 

 Koch ; Ch. robertsoni, Brady). — 23, 

 Magnified sketch of ditto, from figure 

 by Prof. Robin. 



These little animals have a charac- 

 teristic manner of walking, which is 

 neither like that of the cheese mites 

 (Tyroglyphi), nor of the sugar mites. 

 (Glyciphagi). When they advance they 

 have not, like them, the head lowered 

 between their first pair of legs ; they 

 hold it, on the contrary, directed straight 

 in front, their maxillary palpi being always extended, as if to be 

 ready to seize and embrace any prey they might meet. Then, 

 in place of walking like cheese mites, or nmning like the sugar 



Cheyletus eruditus (male). Copied 

 from Fumouze and Robin's figure. 



