266 



PARASITES OF MAN 



herpetic patient have been described as new to science by M. 

 Bogdanoff, but Megnin points out that these Acari are only 

 female and young male representatives of his Chorioptes seti- 

 ferus (var. bovis) respectively. In Newfoundland, Dr Le Hoy de 

 Mericourt discovered a singular species upon an officer who 

 had come from Havannah (Tyroglyphus Mericourti, Laboulbene). 

 It possesses enormous palpi, as in the genus Chyletus to which 

 Kobin refers it. Another ectozoon, placed by Megnin and 

 others amongst the lowest types of Arachnida, is the well- 

 known Dertiodex folliculorum. It is a gregarious species, a 



Fio. 53. Demodcxfolliculorvm, var. caninus. a, Female ; b male. Viewed from below 

 and in profile. Magnified 300 diameters. After Megnin. 



dozen or more examples often being present in a single dilated 

 hair follicle. Though disfiguring to the human face it pro- 

 duces little harm. M. Gruby made it out to be a very common 

 parasite, infesting forty out of sixty persons ; but Megnin, in 

 his brochure (1. c. infra, p. 119), shows this statement to be an 

 exaggeration. It infests on the average not more than one in 

 ten persons. According to Gruby, moreover, a single follicle 

 in the dog may contain 200 of these mites, another statement 

 which Megnin deems unreliable. The Demodcx of the dog is only 

 a variety (fig. 53). Many other human Arachnids have been found, 

 some of which appear to be genuine species, whilst others aro 



