10 VETERINARY PARASITOLOGY 
hidden under the body, so that from the dorsal aspect 
only two pairs are visible. 
2. Psoroples.—These are comparatively large oval- 
shaped parasites, just visible to the naked eye when 
viewed against a black background. The legs are long, 
and all are visible from the dorsal aspect. The suckers 
are carried on long trumpet-shaped_three-jointed 
pedicles, and are absent in the female on the third pair 
of legs and in the male on the fourth pair. The rostrum 
is long and conical. The posterior extremity of the 
male bears two triangular abdominal prolongations, 
each of which bears five bristles. These are the copula- 
tory suckers, and are absent in the female. 
3. Symbiotes. — These, again, are oval in shape. 
The legs are long and thick, but the posterior pair is 
poorly developed and placed ventrally,so that,on viewing 
the parasite from the dorsal aspect, only three pairs are 
visible. The suckers are carried on short, broad, 
unsegmented pedicles. 
The rostrum is short and is broader than long. The 
male carries square abdominal prolongations, each 
bearing five bristles, and in the female these are rep- 
resented by two short cylindrical projections. The 
Symbiotes show a serrated edge, and the body is usually 
mapped out by broad lines, which extend from the 
proximal margins of the legs. 
4. Demodecide.—These will be described when dis- 
cussing follicular mange in dogs (p. 21). 
Symptoms and Diagnosis of Mange.—The first sign 
of mange noticeable in any animal is a hyperemic 
condition of the skin, accompanied by the usual signs 
of skin irritation, such as scratching and rubbing the 
part. Gradually the hair is lost and the epidermis 
becomes thickened, and a collection of scales may appear 
cn its surface. The desquamated epithelium soon 
becomes caked together by exudate and blood into 
