OX WARBLE ELY OR BOT FLY. 
11 
In some observations taken by Mr. A. C. C. Martyn, Agricultural 
College, Aspatria, Cumberland, in 1885, of which he sent me notes, he 
found that the full-grown maggot squeezed itself out of the warble in 
the morning, or at some time between six o’clock in the evening and 
8 a.m. the following day. This point he ascertained in the course of 
his experiments in rearing the chrysalis ; in these he found the 
maggots leaving the warble stuck fast, or trapped, as the case might 
be, on bird-lime, or in the little bags fixed for them to drop into, in 
the morning, but never in the middle of the day. 
In the case of eighteen specimens watched by Mr. Martyn, the 
chrysalis stage lasted about twenty-five days; but, to ascertain the 
effect of cold on rate of development, four chrysalids were put by them¬ 
selves at a much lower temperature. These developed into flies 
(scientifically speaking, the pupse developed into the imago-state) in 
an average of thirty-six days (that is, took ten days longer in develop¬ 
ment than the others), and the flies were not such fine specimens, not 
so large or well marked as the others. 
The Ox Warble Fly, or Bot Fly (scientifically, the Hypoderma 
bovis), is a two-winged fly, upwards of half-an-inch in length, so 
banded and marked with differently-coloured hair 
as to be not unlike a Humble Bee. The face is 
yellowish ; the body between the wings yellowish 
before and black behind ; and the abdomen usually 
whitish at the base, black in the middle, and 
orange at the tip. The head is large ; the -wings Fig. 14.—Ox Warble 
brown; and the legs black or pitchy, with lighter F1 y- 
feet. There are, however, some slight differences in colouring, and 
amongst those reared by Mr. Martyn, in the case of five out of the 
twenty-five, the portion of the abdomen beyond the transverse black 
baud was grey instead of yellow or orange. 
The female fly has an ovipositor, or egg-laying tube, formed of 
telescope-like joints, and ending not in a point for piercing with, but 
a trifid extremity beset with small hairs (see p. 4). The egg-laying 
season is mostly in the warm part of the year, but as the time of 
presence of the maggots extends (as shown by trade reports of con¬ 
dition of hides) from February to September, so also must the exist¬ 
ence of Warble Flies, to which these warble-maggots turn, extend 
to some degree over many months, and the date of egg-laying vary 
conformably. 
Process of formation of the Warble. 
The early part of this operation, including the minute maggot no 
thicker than a hair going down to the under part of the hide, and there 
lying feeding in the little bloody sore which it has caused, has been 
described, so also has its growth, until (tail uppermost) it lies in the 
