Sarcoptidcs Psorica. 159 



paratively easy to reach them by local dressing so that they are 

 much less inveterate than the sarcoptes. 



Symbiotes. (^Chorioptes, Dermatophagus) . These have an 

 ovoid body, rounded at both ends, bilobed or simply notched 

 posteriorly in the male ; rostrum conical, as broad as long, devoid 

 of cheeks, mandibles thick, short, pincer-like, palpi in three seg- 

 ments ; legs thick, long, visible beyond the edges of the body, 

 and with bell-shaped ambulatory suckers on short pedicles. 

 Male has copulatory suckers. 



Like the psoroptes, the symbiotes live on the surface shelter- 

 ing under hairs and scabs. Their favorite habitats are the hol- 

 low of the pastern and digital region in horses and sheep, and 

 the root of the tail in the ox, and for years they will confine their 

 ravages to these points. When of old standing and over- 

 crowded they may extend to other parts. From the limited area 

 of their invasion and their life on the surface they are easily 

 controlled by local dressings. 



LIST OF PSORIC SARCOPTID^. 



In the following table the species under each primary division 

 are sub-divided into the varieties which confine themselves more 

 or less strictly to given genera as hosts : 



Sarcoptes Scabei. Two pairs posterior legs incomplete in 

 the female ; the third pair only in the male. Dorsum with 

 many sharp pointed papillae. 



Sarcoptes Scabei varietas Hominis. Man. 



Sarcoptes Scabei varietas Equi. Horse, ass, mule. 



Sarcoptes Scabei varietas Caprae (5". Rupicapnz') . Goat. 



Sarcoptes Scabei varietas Ovis. Sheep. 



Sarcoptes Scabei varietas Siiis (5". Squamiferus) . Swine. 



Sarcoptes Scabei varietas Lupis. Wolf, fox, dog, deer, man. 



Sarcoptes Scabei varietas Cameli. Camel, llama, giraffe, ante- 

 lope. 



Sarcoptes Scabei varietas Canis. Dog. 



Sarcoptes Scabei varietas Hydrochoeri. Ferret. 



S. Notoedres. S. Minor. S. Maris. S.Cati. Cat, rab- 

 bit, rat, mouse. Anus dorsal, with midulating concentric eleva- 

 tions.. 



S. Mutans. S. Vulpis. Feet, comb, wattles, angle of 



