WARBLE FLY. 
99 
endeavour to describe the changes, both in external form and internal 
structure, which it passes through so rapidly (from the time it is first 
noticeable in the opening warble until it gains the shape in which it 
is best known), that little notice appears as yet to have been taken of 
the details. 
Fig. 1. 
Fig. 1.—Channel through hide, much magnified. 
The commencement of the attack* had been noticed in the previous 
November in the form of small inflamed patches or swellings on the 
flesli-side of the hide, within which the maggot lay free—that is, not 
enclosed in a cell—and down to which swellings a fine channel passed 
from the upper surface of the hide. 
This channel appeared to have no lining membrane, but to be 
merely a passage gnawed or torn by the mouth-hooks of the maggot, 
and (as in fig. 1) sometimes slanting, or taking a straight course, or so 
completely curved at the upper part of its course that it was impossible 
that the channel where this curve existed could have been formed by 
the ovipositor of the fly; consequently, as the method of egg-laying 
may be presumed not to vary, to all appearance proving that the egg 
from which the maggot hatched was laid either outside or just beneath 
the outer cuticle of the hide. 
Careful watch was kept both on living cattle and newly-flayed hides 
in various localities throughout the winter, in order to secure the date 
of the first appearance of the warble in its open condition, which took 
place (generally) from about the 14th to the 25th of February. The 
first advance on the condition of a mere liair-like streak through the 
hide was found in specimens cut from the hide of a young bull, and 
sent me by Mr. John Dalton, of Wigton, on Jan. 27tli. In these there 
was the first appearance of the warble as a perforated swelling , with 
the maggot of a clearly distinguishable size within. The channel 
through the hide was still very small, the opening on the outside being 
about as large as the prick of a common darning-needle, and below, 
though larger, scarcely the sixteenth of an inch across. 
This perforation, or maggot-gallery, was somewhat cone-shaped, 
with smooth , white, shiny walls. These conditions are important to be 
* This is described in my ‘ Eighth Eeport on Injurious Insects,’ p, 115. 
