and Warble Maggot. 
495 
pomonella, Walsh, described by Professor H. Comstock in the 
Report of the Department of Agriculture U.S.A. for 1882, p. 197. 
There it is noted that each of the spiracles he describes " is 
expanded into a plate, the free margin of which is fringed by a 
double series of cylindrical projections about twenty in number. 
With a very high power of the microscope the distal end of each 
of these projections appears to be sieve-like, an arrangement 
which doubtless prevents the entrance of any foreign matter 
into the respiratory system." Whether in the case of the warble 
maggot the spotted or sieve-like appearance is given by micro- 
scopic hairs placed to preserve the entrance free, or by other 
structures, I could not ascertain on account of the excessive 
minuteness of the organs ; but a fringe of this nature is to be 
found in some forms of spiracle, and the use of such an 
apparatus to guard the entrance of breathing-tubes, when acting 
in a passage which is being formed in living hide, is obvious. 
Fig. 7. — Full grown 
Maggot, under side, 
much magnified. 
Fig. 8. — Spiracle 
Tube {one of the 
pair), much mag- 
nified. 
Fig. 9. — Discs at ex- 
tremity of Spiracle, a 
seen loitli \-in. object 
glass. 
Up to the time when the moult takes place to the final form 
of which I am now speaking, these spiracles are buried up to 
their disc-covered tips in the tail end of the maggot ; but then 
they are cast off entirely with the moulted skin, and in the 
newly exposed skin beneath we find the first appearance of 
spiracles of the well-known kidney shape, but Avith the surface 
more radiated, and of a paler chestnut colour than in their later 
condition. 
During the spring investigations I had an opportunity more 
than once of observing and also securing both the moulted skin 
containing the early form of spiracle, and likewise the proprietor 
maggot, bearing the new kidney-shaped pair ; and also, in one 
instance, secured the maggot when about to moult off the old 
