Internal Parasites of Sheep . 
87 
Western Highlands, and in the western-most counties of 
England. In these districts they are usually found on sheep 
from March till September. Beyond the immediate effects of 
skin irritation, the tick is sometimes credited with introducing 
the germs of a disease known as “ louping ill ” and also other 
diseases. 
Dipping, as for scab, is effectual both as a cure and preventive, 
and the other measures indicated for destruction of the tick of 
cattle should be adopted. 
Scarlet Mite or Harvest Bug. — This minute parasite, the 
larva of the Trombidium holosericum , of the Order Acarina , 
is sometimes found in the late summer and early autumn 
attacking the inside of the thighs and forearms of sheep. It is 
just visible to the naked eye, about one-twentieth of an inch 
long, and of a reddish colour. In some seasons this parasite 
induces considerable irritation. The infested sheep is noticed 
to be uneasy, tries to reach its forearm and neck with its hind 
feet, and nibbles the skin on the inside of the legs. The 
irritation lasts only two or three weeks — the period which the 
residence on the animal “ host ” occupies, for the adult 
parasite is believed to live on vegetable matter. It cannot be 
regarded as a very common or very important parasite. It is, 
however, capable of inducing symptoms which at least might 
suggest scab, and it is well, therefore, to take cognisance of 
it. The application of sheep dip or a very small quantity 
of mercurial ointment stops the irritation. 
Internal Parasites of Sheep. 
Sheep Warble or Bot Fly. — This small, yellowish grey, 
slightly hairy fly ( CEstrus ovis), two-fifths of an inch long, 
with transparent wings, and of a silky hue, lives in summer, 
and is remarkable for its rapid flight. It deposits its eggs 
or larvae in or about the nostrils of the sheep. At this time 
sheep are noticed to bury their heads, to rub their nostrils, 
especially between their forefeet, and sometimes to sneeze and 
snort. The larvae gain the air sinuses or cavities of the head, 
and reside there about nine or ten months. Ordinarily there 
are but a small number of bots in these situations, and no 
symptoms are observed during the winter, but occasionally the 
larvae are very numerous, and by their gradual growth the 
whole mass may press on the part and interfere with breathing. 
Symptoms . — It is in the early summer, when the larvae 
are leaving their winter quarters for the outer world, that 
symptoms are sometimes very marked. When the larvae are 
creeping down from the sinuses in considerable number, there 
is much sneezing, a discharge from the nostrils, and coughing ; 
the eyes stare and are blood- shot ; the sheep may stagger as 
