222 THE ARACHNOIDS. 



The Trombidiidae. 



These generally have a soft integument and are often brightly colored. 

 A very common and annoying member of this family is the hexapod larva 

 of the Trombidium holosericeum. It is usually designated Leptus 

 autumnalis. Popularly it is termed "harvest mite," "red bug" or jig- 

 ger. They are found in the fields in the autumn and attack both man 

 and animals. The itching and redness produced is at times called 

 autumnal erythema. There is a Trombidium in Mexico which has a 

 predilection for the skin of the eye-lids, prepuce and navel. The Ked- 

 ani mite is believed by the Japanese authorities to bring about infection 

 with Japanese river fever or Tsutsugamushi, as the result of trans- 

 mitting either a bacterium or protozoon by its bite. The disease some- 

 what resembles typhus, although an eschar at the site of the bite and 

 lymphatic involvement is present. Of the Gamasidae, which generally 

 have a hard body, only the Dermanyssus gallinae is of interest. This 

 coleopterous mite infests chicken-houses and sucks the blood of the 

 inmates. They will also attack man. Poultrymen may be troubled 

 w r ith a sort of eczema on the backs of the hands and forearms, similar 

 to scabies, resulting from bites by these mites. They measure 350 x 650^. 

 They have no eyes. 



Tyroglyphidae. 



Mites of this family live on cheese, flour, dried fruits, etc. They are 

 chiefly of importance because of their being occasionally found in 

 urine, faeces, etc., and being striking objects, the question of pathogen- 

 icity arises. The T. longior has been associated with intestinal trouble 

 (probably a coincidence, patient having eaten cheese containing these 

 mites). 



Glyciphagi are found in sugar and are the cause of what is known 

 as "grocers' itch." Rhizoglyphus parasiticus is reported to be the 

 cause of an itch-like affection of the feet of coolies on tea plantations. 

 To distinguish: the dorsum of Glyciphagus is hairy or plumose; that 

 of Tyroglyphus has both claws and suckers on tarsi, while Rhizoglyphus 

 has only claws. 



