THE ACAEINA OR MITES. 



121 



readily, and it has been noted that the species common on birds of prey are not like 

 those found on the victims of these birds. Ewing has found that the mites Avilf live 

 for three days after removal from their host. 



These mites were for a long time kept in the genus Dermaleichus Koch, but tliis has 

 been shown to be a s\Tion\Tn of Analges Nitzsch, 1818. Many other genera have been 

 formed in recent years, and a revision of the family by Canestrini, in " Das TieiTeich, " 

 in 1899, includes 31 genera and 7 subgenera. Several, however, are based on very 

 slight cliaracters, and do not appear advisable. 



But few species have been recorded from tliis country-. Mr. T\Trell and Prof. 

 Haller described several from Canada, and Dr. Trouessart has taken some from Ameri- 



FiG. 2-i9. — PtcroUchus sp. (near delibatus), on 

 condor. (Author's illustration.) 



Fig. 250. — Hypodcras col- 

 umhae, a stage of Falcul- 

 ifer: a, h, c, Epimera. 

 (From Kellicott.) 



can birds in the Paris museums. Various classifications have been made by different 

 Gbser\'ers; Trouessart proposed a simple armiigement of genera in tlxree groups, as 

 follows: 



Analgesese: Anterior legs with spines; females with tip of abdomen entire. 



Genera: Analges, Protalges, Analloptes, Xolalges, Megninia. 

 Pterolichese: Anterior legs unarmed; females with tip of abdomen entire. 



Genera: Freyana, Fterolichus, Protolichus, Pseudalloptes, Xoloptes, Pter- 

 onyssus. 

 Proctophyllodese : Anterior legs unarmed ; females with tip of abdomen divided . 



Genera: Proctophyllodes, Pterodectes, Alloptes, Pterocolus. 



Oudemans has proposed a new arrangement of tliis group (wliich he calls Acaridse) 

 based on the presence or absence of vertical hairs on the cephalothorax. By using this 

 with the characters previously known he makes 18 subfamilies. These vertical hairs 

 are, no doubt, of value in classification, but can better be utilized to define genera 

 rather tli.an as a prime divisory character in a superfamily. In some species these 

 erect hairs are short and minute, so that they are easily overlooked. Two genera have 

 but one (a median) vertical hair. 



In the table following I have included all known from the United States and Canada, 

 and most of the larger genera that are apt to be found here. 



