THE COMMON SHEEP-SCAB. 69 
great care should now be taken to stamp it out, and prevent 
other flocks from becoming infested. Our farmers, and 
chiefly those that are still unfamiliar with the details of 
sheep husbandry, can not be too careful in regard to this 
disease. Wherever sheep husbandry has been well estab- 
lished for some time, and where farmers have learned to cure 
the disease, the losses caused by scab are gradually reduced 
by the proper use of remedies, and by the exercise of good 
judgment in furnishing their animals sanitary surroundings. 
This scab-mite can be more completely and readily extermi- 
nated than many of the other parasites of sheep. 
The mite is very small, barely visible to the unaided eye; 
it has an elongated oval body, resembling in shape a turtle. 
Its skin shows numerous small wrinkles, and iscovered with 
spines, hairs, scales and wart-like projections. The mature 
mite has eight legs, each composed of five joints. The illus- 
trations (fig.38, 39 and 26) show the male, female, and the 
mouth parts. The male (fig.38) upper side, is quite different 
from the female (fig. 39), ascan be readily seen by comparing 
the illustrations. The young larval mite possesses but six 
legs. Both males and females make burrows or tunnels in 
the skin of their host, but those of the former are always 
very short. 
Neither sex lives longer than from three to six weeks, but 
during this time the female is almost constantly engaged in 
laying eggs. Theseare smooth objects, of an elongated oval 
shape, and are deposited in small patches, each containing 
from twenty to twenty-four eggs, which hatch in the course 
of four to seven days. The six-legged larva undergo three 
moults in the tunnels, and reach maturity in about fourteen 
days, when they leave their old quarters and start tunnels 
for their own use. Gerlach computed that a single female 
could produce in three months a progeny of 1,500,000, He 
gives the result in a tabular form: 
First generation after 15 days produces 10 females and 5 males. 
Second “ Eh Re 100°. 4 Ea pey 
Third “ Card g a te hc ots DOU mE 500 
Fourth  “ eee th 1 OCOO0 yn a? 8,000. 
Fifth fe flirted! O024700,000 -* ‘50,000. °'« 
Sixth - on (9) "Ff. ‘* 1,000,000 ‘* 500,000 f 
