690 MEDICAL ENTOMOLOGY 



gives rise to considerable irritation and even vesication. It is a mite of 

 this family which, in the larval stage, is believed to be the transmitting 

 agent of Japanese River Fever. 



Trombidium holosericeum, L., is the common European species, and is 

 widely distributed. Recently Bruyant has pointed out that two distinct 

 species have in the past been confused with holosericeum, namely, 

 T. rimosum, Koch, and T. latum, Koch ; they can be distinguished from 

 one another by the character of the furrows on the cephalothorax and 

 by the shape of the dorsal hairs. 



FAMILY HYDRACHNIDAE 



Body short and almost spherical, without any division into cephalo- 

 thorax and abdomen. Legs arise close together and consist of seven seg- 

 ments. One or two eyes on each side of anterior end of body. Mouth 

 Parts not carried on a rostrum ; suckers usually present near the genital 

 openings. Living in fresh water. 



This family contains the fresh water mites, several of the species of 

 which, in their larval stages, are often found attached to the neck and 

 abdomen of adult mosquitoes, particularly anophelines. They belong 

 to the genus Hydrachna : their life histories are unknown. 



FAMILY SARCOPTIDAE 



Body as a rule soft ; palpi small and three-jointed. Ventral suckers 

 Present at genital opening or near anal opening. Eyes wanting. Legs 

 consisting of five segments ; tarsi often end in suckers. Stigmata wanting. 

 Adult often parasitic. 



Banks, in his Treatise on the Acarina, places these mites in the 

 superfamily Sarcoptoidea, which he divides into seven families. His 

 superfamily is here retained as a family and the families as subfamilies. 

 He gives the following key for their identification: 



BANKS' KEY TO THE SUBFAMILIES OF THE SARCOPTIDAE 



1. With tracheae ; no ventral suckers ; legs ending in claws ; body 



divided into cephalothorax and abdomen ; the female with a 

 clavate hair between legs I and II ; not parasitic on birds 

 or mammals . . .''-.". . .. . . . Tarsoneminae. 



Without tracheae ; no such clavate hair . . . .,",. . 2 



2. Genital suckers usually present ; not parasitic on birds or 



mammals ; skin usually without fine parallel lines . . . . , . 3 

 Genital suckers absent ; parasitic on birds or mammals ; skin 

 with fine parallel lines . , , . . ; ' ; . ' . , ,4 



