Ewing — Significance of Parasitism in Acarina. 23 



is by means of the statistical method, lists of the parasites 

 with more than one host species having been prepared. In 

 some groups a complete list of all the known parasites with 

 the host or hosts of each is given. The second method is 

 by experimentation by means of which data were ob- 

 tained; in regard to the ability of the parasites to move 

 about when detached from their hosts, in regard to the 

 length of time a parasite can live when detached from its 

 host when either with food or without food, the habits of 

 the parasites themselves, and lastly and most important 

 of all, transfers of the various parasites from their normal 

 hosts to various other hosts. 



In the following pages of this chapter the different 

 groups of the parasitic forms will be taken up separately; 

 the list of species with their hosts being given first, after 

 which follow the deductions obtained from a study of 

 these lists, together with what experimental evidence I 

 have secured. 



The first group with which we will occupy our atten- 

 tion is that of the parasitic Cheyletidae, a list of them 

 being given with the hosts of each. 



A List of the Parasitic Cheyletidae and Theie Hosts. 



MYOBiA Hey. 



M. lemnina (Koch) — Arvicola arvalis Pall. 



M. caudata Banks — Little brown bat. 



M. miisculi Schrank — Mus musculus, M. silvatlcus L., M. rattus. 



M. hrevihamata Haller — Miistela vulgaris. 



M. pantopus Troues. — Synotus barbastellus. 



M. heteronycha Berl. & Troues. — Phyllorhina tridens. 



M, poppei Troues. — Vesperugo abramus. 



M. chiropteralis Michael — Rhinolophus hlpposideros. Vesperngo pipls- 



trellus. 



PICOBIA. 



P. Jieeri Guzzoni. 



SYEINGOPHILUS Hel. 

 8. hipectinatus Heller — Phoenopepla nitus Sev. 



PSORERGATES Sty. 

 P. simplex Tyrrell — Mus musculus, Arvicola agrestls. 

 P. simplex var. musculinis. 



