15 
swellings, known as Warbles, with a little mercurial 
ointment as soon as ever it is perceptible to touch and the 
opening has formed, thus destroying the maggot within 
whilst the sore is beginning, instead of after it has been 
established several months; but it will be desirable to 
consider the whole of the attack, and especially the 
reason why the maggot-cavity does not unite thoroughly 
(even though it apparently heals) if left till February or 
March. 
This Ox Bot Fly is about the same size, or rather larger 
than, the previously-mentioned Bot Fly of the horse. It 
has a hairy body and large head, with yellow face. The 
fore body has four raised lines along it, and the abdomen 
is white or yellowish towards the base, black in the 
middle, and orange at the end. The legs are black, with 
red feet, and the wings are brownish and unspotted, and 
with two large alulets. 
The duration of the attack is from one summer to 
another. It may begin in May or June, or later, accord¬ 
ing to whether the cattle are in low ground or on hills, 
and according to other circumstances of weather, &c., 
but from one summer to another gives the best general 
idea of its whole duration. 
The egg is of an oval shape and white, with a small 
brownish lump-like appendage at one end. There has 
been much scientific discussion whether the egg is laid 
on the cattle or inserted into the skin : it does not seem 
proved either way ; but the most recent observations 
point to it being placed externally either on the skin or 
on the hair, and, in the case of the nearly-allied Warble 
Fly of the reindeer, the female Fly has been distinctly 
seen with the egg at the end of the ovipositor in the act 
of placing it on the animal. The common idea that the 
wild gallop of the herd when attack is going on is caused 
by the intense pain of the hide being pierced is not well 
founded, for various reasons to be referred to presently. 
The warble-maggot, in the early part of its life, is 
white and transparent and smooth. It makes its way 
into the lowest parts of the skin, and lies there harm- 
