WARBLE FLY. 
101 
maggot found on Jan. 27tli tliere was the apparatus for cutting or 
gnawing. 
The duration of special habits of life in the maggot may be divided 
into three periods : that above mentioned, when its chief work appears 
to be making its way down ; the next, when it starts into the active 
state which precedes its first obvious appearance in the opening warble, 
and in which its most important work is forcing its way up again, tail 
foremost; and the third, in which, having formed the opening, it lies 
within feeding, mouth-end downwards, in the filthy discharge its 
own presence causes, until it is ready to leave the hide, and turn to 
the chrysalis-state. 
The method by which the perforation is effected has given rise to 
much ingenious speculation ; but, by carefully watching the habits of 
the young living maggots, and likewise the condition of the perforation 
in fresh hide during the very short time which is occupied by the first 
formation of the perforated swelling known as the warble, the whole 
process appears clearly traceable. 
The tip of the tail of the maggot, which is of necessity the point 
of the wedge that precedes its owner up the hide, is not now ended, 
as in its la,test state, by two flat, kidney-shaped spiracles (fig. 4) ; 
whilst the boring work has to be done, the spiracles are of a different 
form. They are, during this time, somewhat club-shaped, or, when 
highly magnified, appear like short bent cylinders (fig. 7, overleaf). 
These are of horny or cliitinous materials, and each of the pair of 
spiracles, or breatliing-pores, is placed at the extremity of a large 
Fig. 4. Fig. 5. 
Fig. 4.—Latest form of spiracles, much magnified. Fig. 5.—Spiracles and 
trachea of young maggot, much magnified. 
trachea or breathing-tube, which pair of tracheae are tied together by a 
transverse tube placed near the spiracles. The maggot is thus 
provided (fig. 5) with a compact, hard-tipped apparatus, very suitable, 
i 
