PARASITES AFFECTING THE SKIN 47 
painful elevations about the size of a hazel-nut appear 
on the skin of the back and arms. In each of these is 
a “warble.” At the summit of each elevation is a 
small hole, and the larva applies its posterior extremity 
with its ‘ breathing-holes”’ to this. In June the larva 
emerges through this apical orifice, after it has become 
enlarged. The ‘“‘ warble’? now becomes buried under 
leaves or straw, and after passing through the chrysalis 
stage, finally develops into a fly. 
The larva is brownish in colour, and composed of 
eleven rings. In shape it is conical, and much resembles 
a “bot.” The head bears two hooks for anchoring, 
arranged at right angles. The spines are arranged in 
three rows on each side, leaving out the centre portion, 
except in the last two segments, which are unarmed. 
The lateral prominences consist of an upper and lower 
in each segment, and are well marked. 
When mature, the larva measures 22 millimetres to 
28 millimetres in length, and about 15 millimetres in 
breadth at the widest part. 
Treatment is usually unnecessary. If desired, the 
elevations may be coated with salicylic acid, or iodoform 
collodion, or even Stockholm tar. These suffocate the 
parasite by closing the air-holes. 
When the larva is ripe, it may often be squeezed out, 
especially if the skin over the elevation is first slightly 
nicked with a bistoury. 
Prevention is of more importance. The backs of 
cattle should be dressed during the months the fly is 
active with a mixture of sulphur, ol. picis, train-oil, and 
rape-oil, at least once weekly, to ward off the attacks 
of flies. 
Hypoderma Equi (Loiset).—This parasite is found in 
Holland, Belgium, and France. It produces cutaneous 
tumours containing a larva, and in all its characteristics 
much resembles Hypoderma bovis. 
