WABBLE FLY. 
107 
in more numerous bands, than are noticeable in the previous stages. 
The prickles are now strong enough to cause an unpleasant sensation 
when the maggot crosses the hand, and to play an important part in 
its locomotive powers in its cell, and in the effect on the tissues caused 
thereby. The visceral contents are now thick, and obviously formed 
of the filthy matter which is caused by the perpetual irritation of the 
suction of the mouth-end of the maggot at the bottom of the sac. It 
is also now furnished with a small curved caudal aperture, placed 
nearly between the spiracles (see fig. 4), from which some slight 
amount of discharge of contents can take place. 
These are the main differences connected with the moult to the 
final form of the maggot, and, following on these alterations in its 
structure, and especially on the power of keeping up a constant irrita¬ 
tion by means of the muscular expansion and contraction of its 
prickly skin, we find the lining membrane of the cell increasing in 
thickness, until it becomes well defined as a tough wall round the 
perforation, continuous with the upper part of the cell. Fig. 15 shows 
a cell drawn in section, and slightly magnified after maceration in 
water. The lowest end of the maggot-chamber appears full of foul 
matter, caused by the irritation of the 
friction and suction of the maggot; and, 
after the creature has crawled from its 
hole, a pressure on the empty warble is 
followed by a discharge of some amount 
of purulent matter. 
When the maggot has gained the 
condition mentioned above it undergoes 
no further great change until it turns to 
the chrysalis-state. The spiracles become less radiated and darker, 
the maggot also becomes darker as it increases in size ; but the main 
points of its life now are to form, at the expense of the animal in 
which it lives, the material from which the fly will presently be 
developed, to start (unless means have been taken to prevent it) the 
next season’s attack on the herd.”* 
When the warble-maggot is about to change to the chrysalis-state, 
it squeezes itself out, tail-end foremost, from the warble, and, after 
falling to the ground, creeps to some shelter where it turns to 
* 
chrysalis, from which in due time the fly comes out. These changes 
have previously been described, but the following notes, by Mr. A. C. 
C. Martyn, Agricultural School, Aspatria, add some useful information 
from personal observation, as confirming previous statements that the 
Fig. 15.—Warble-cell, slightly 
larger than life. 
* “ Observations on the development of Ox Warble and Warble Maggot,” by 
Eleanor A. Ormerod, ‘Journal of the Royal Agricultural Society,’ vol. xxi., 
part ii., 1885. 
