48 BOARD OF AGRICULTURE. 
Mange-insect of the Horse (Psoroptes equi Gervais). 
This insect is readily visible to the naked eye and swarms 
on horses afflicted with the mange, which is a disease anala- 
gous to the itch inman. It has a soft, depressed body, spiny 
beneath at the base of the legs and on the thorax. One or 
both of the two posterior pairs of feet bear suckers, and all 
are more or less covered with long slender hairs. 
Figure 45. 
Fig. 46. 
This insect may be destroyed by the same remedies used for 
lice and for the human itch. The best remedy is probably the 
solution of sulphuret of potassium, described on page 109. 
The Itch-insect (Sarcoptes scabiet Latr.). Figure 47. 
This is a very minute, whitish species, barely visible to the 
naked eye, unless on a dark surface. It has been, in former 
times, the subject of many lengthy discussions, in reference 
to its causing the itch. It is, however, at the present time 
fully ascertained to be the sole cause of the ordinary itch, 
though other species of similar parasites may cause different 
varieties of itch. The body is rounded and soft, with small 
round pustules on the middle of the back, and with radiating 
lines or ridges, the sides of the body and legs bearing long 
bristle-like hairs. The mandibles are needle-like. The 
female is largest and has the two pairs of hind legs but little 
developed, ending a bristle ; in the male they are well devel- 
oped and terminate ina slender sucker. These creatures, as 
seen under the microscope, have something of the unwieldy 
Figure 45.—Psoroptes equi Gervais, female ; ventral side, much enlarged. 
Figure 46.—Head of the same, more magnified. Both from Cuvier. 
Digitized by Microsoft® 
