as to become exceedingly rigid, and so transparent that much 
of the internal structure could be seen plainly. The rigid 
glassiness of the young maggot favours the presumption that 
it forces itself up the channel from the sub-cutaneous tissues 
to the outside of the hide, small end foremost, with its first 
spring growth, and gradually enlarging the hole by the 
pressure of its own hard, inflated, and rapidly changing- 
condition, forms the warble hole. The upper part of the 
passage is not torn or ulcerated as below. Disorganised tissue 
and ulcerated matter are sometimes dragged into the channel 
by the maggot, and in the opening of the warble we sometimes 
find a slight coating of gummy matter on the tip of the 
maggot; but the great mischief from disorganisation, swelling, 
and inflammation is done beneath the hide. 
The conditions of the very young maggot named above, 
combined with the peculiar shape and pointed ends, adapts 
them perfectly in the first stage for travelling, in the second 
for pushing themselves up small end foremost, armed with 
minute hard spiracles, through the opening warble. The above 
changes in condition are rapidly gone through, and when the 
maggot has gained about a quarter or a third of its growth, the 
spiracles are developed into an angularly kidney-shaped form, 
and the maggot assumes the compressed oval shape in which 
it is best known. It is still white, but opaque, with the seg¬ 
ments well marked. It has no occasion now to bore its way, 
and ceases to be provided with a form fitted for perforation. 
Miss Ormerod found by microscopic investigation that the 
spiracles have two, and she thinks three, different successive 
forms before developing into the last state; and they also 
differ from each other in the amount of spiracle exposed at 
tip of grub. The breathing apparatus consists of a trachea or 
breathing tube from each of the spiracles, and from each 
trachea a series of lesser and lesser tubes carries the air 
through the maggot. The two principal tracheae are con¬ 
nected together near the spiracles by another short tube, 
which forms a channel of communication, and thus ensures 
air being supplied to the maggot if one spiracle should be 
choked. In a short time the maggot is to be found advanced 
to its oval form, and the passage through the hide to be then 
covered with a coating of membrane. 
