80 
GEORGE MULLER. 
lias these suckers on the first, second and fourth, and the female 
upon the first and second pairs of feet. 
The parasites burrow into the succulent layers of the stratum 
mucosum, and derive their nourishment from its cells. They are 
communicable to man , and may cause the itch. 
Of these sarcoptous insects we have: 
Sarcoptes scabiei , found in the skin of man, horses, Neapolitan 
sheep, and lions. 
Sarcoptes squamiferous , found in the skin of dogs, pigs, 
sheep, goats, and probably men (Zurn.) 
Sarcoptes minor , found in the skin of cats and rabbits. 
A tendency has been apparent lately to unite sarcoptes scabiei 
and sarcoptes squamiferous in a single species under the name of 
sarcoptes scabiei communis. And, in fact, the points of differ¬ 
ence between S. scabiei and S. squamiferous are not important, 
and certainly are not constant (Zurn, Johne.) 
2. Dermatocoptes , Saugmilben, 0.5-0.8 mm. long, 0.3-0.5 
mm. broad, have a body whose dorsal surface is covered with 
hairs and spines, a long head, long prominent jaws and tulip¬ 
shaped sucking disks upon the ends of all four pairs of feet in 
the male and on the first, second and fourth pairs in the female. 
They live upon the cutaneous surface, especially where the 
hairs are thick, without burrowing into the skin. They obtain 
nutriment by sucking, by means of their mouth apparatus, fluid 
from the rete malphigi and the lower layers of the cuticle. They 
cannot cause the itch in the human skin. 
Of Dermatocoptes we have: 
Dermatocoptes communis , found in horses, cattle and sheep. 
Dermatocoptes cuniculi , found in the external auditory pas¬ 
sages of the rabbit. 
3. Dermatophagus , Schuppenfressendemilben, 0.3-0.5 mm. 
long, 0.2-0.3 mm. broad, with bluntly-pointed head, two scissor- 
shaped jaws, long feet and cylindrical sucking discs, found in the 
male upon all four pairs, and in the female in the first, second 
and fourth pairs. The male also has posteriorly two other bodies, 
each one formed of two bristles and a sword-shaped chitinous 
body; and the female has two cylindrical processes and a few 
bristles at the same place. 
