LIFE-HISTORY OF WARBLE FLIES. 1438 
These distinctions, however, are difficult of observation, excepting 
by those used to the work, and the important, and really very extra- 
ordinary, difference between the two kinds, so far as the U.S.A. observa- 
tions show at present, lies in the method and locality of development of 
the larva in its earliest stages. 
It is considered as established, by the writer and editor of the paper 
above quoted, mainly on the authority of skillel and minute observa- 
tions by Dr. Cooper Curtice, D.V.S., that the early part of the infesta- 
tion is conducted as follows :— 
The eggs of the H. lineata, which much resemble those of our boris 
(see figure at heading, p. 184), are laid in rows up to as many as of 
ten eggs in number on the hairs of the cattle, for the most part on the 
hairs near the heel (whence the name of ‘‘ Heel Fly’), or, if laid else- 
where, mostly on the flanks or legs near the heels. By means of the 
licking of the cattle, the eggs, or rather the hatching larve contained 
in them, are considered to be conveyed into the mouth, from whence 
the little maggots pass into the cesophagus, or gullet, and there it is 
considered to be proved that they adhere in some way by means of 
their spines, and pierce through the wall of the esophagus; the larva 
at this time being from eleven to fourteen millimétres long—that is, 
about half an inch. Here it is said to moult off its somewhat prickly 
skin, and take on the smooth skin of its second stage, in which “ for 
eight or nine months it wanders slowly in the tissues of its host.” 
During the late winter it is considered to reach a point beneath the 
skin in the region of the back, and to penetrate it, tail end foremost, 
and then again to moult, this time reassuming a spiny coat, and after 
its long journey to pass the rest of its existence in the way only too 
well known to us in the case of our LI, bovis. 
So far as has lain in my power I have endeavoured to ascertain 
whether the lineata was present here as a known infestation, and 
whether the special points, as that of maggots being observable in the 
cesophagus (or gullet) of cattle, or signs of perforation, were noticeable, 
and also whether any such maggots had been observed in the tissues. 
Hitherto I have quite failed in obtaining information of such being the case. 
Through the chairman of one of our leading butchers’ associations 
especially attending to warble attack, I was allowed to bring the sub- 
ject before the members, but none of them, in the course of dealing 
with carcases under their hands, had observed any such presence; nor 
my own more specially personal enquiry, either with veterinary or 
practical observers, could I find that these points had been observed. 
I enquired very particularly by word of mouth as to observation of 
maggots in the gullet, and I certainly think that, if these occurred at 
the size mentioned (p. 818 of paper quoted), they would absolutely 
certainly have been observed, 
