DESCRIPTIONS OF GENERA AND SPECIES. 201 



Tyroylyphus (part), 1873. Megnin, "Mem. anat. et zool. sur un 



nouvel Acarien de la famille des 

 Sarcoptides, le Tyroglyphus rostro-ser- 

 ratus," in ' J. Anat. pkysiol./ vol. ix, 

 pp. 369388. 



1893. Monier, ' Notes,' p. 453. 



Acarus, part, 1876. Canestrini and Fanzago, " Nuovi Acari 

 Italian!," in ' Atti Soc. Yeneto-Trent/ 

 vol. v, p. 140. 1877, "Intorno agli 

 Acari Italiani," in ' Atti 1st. Yeneto/ 

 ser. v, vol. iv, p. 201. 

 Ansetus, 1898. Oudemans' ' List/ p. 252. 



Tyroglyphidse with the ambulacra of all the legs ses- 

 sile, not pedunculated ; with the mandible not chelate, 

 but consisting of one blade only ; which is usually saw- 

 like, but possibly rarely knife-like. With palpi the two 

 distal joints whereof usually bear a membranous ex- 

 pansion, and the distal joint bears two flagella, usually 

 of unequal length. With a strongly marked division 

 between cephalothorax and abdomen, without anal 

 suckers ; with considerable, but not extreme sexual 

 dimorphism, and with a well-developed hypopial stage. 



This genus, which is the only one in the sub-family, 

 is a wholly exceptional one amongst the Tyroglyphidge ; 

 being strongly differentiated by its saw-like or knife- 

 like mandibles, which contrast sharply with the 

 chelate mandibles of all other genera of the family ; 

 and by the flagella-bearing palpi, the flagella being 

 functional as such ; which again is entirely unknown 

 in any other genus of the family, and probably in any 

 other Acari. The mode of action of these organs is 

 interesting. Megnin was the first author to call atten- 

 tion to the existence of any of these creatures ; in his 

 1873 paper above referred to he says that he found the 

 Acarus H. rostro-serratnm in immense abundance, 

 wading in the thin film of liquid which covered decay- 

 ing mushrooms in the well-known mushroom-cellars of 

 Paris. It is not, however, by any means confined to 

 mushrooms ; it is found on most decaying vegetation 

 of a fleshy nature, particularly underground parts such 



