and Warhle Maggci. 
497 
perforation, show where a small portion of the old and new air- 
tubes (tracheae), belonging to the old and new spiracles, were 
cut through in making the transverse section. 
These air-tubes, like the spiracles at their extremities, were 
now, at this portion of the maggot, in duplicate. This in itself 
is not remarkable, but it is not often that the moult of the 
tracheae can be so perfectly observed. A reference to Fig. 6 
will show the general appearance of the tracheae of the maggot. 
Fig. 12. — Bases of pair of old 
and new Spiracles (vieiced verti- 
cally), much magnified. 
Fig. 13. — Section of Tracheae, 
much magnified. 
with the cross trachea that joins the two main tubes : and on 
making a section across at this point, the old air-tube with its 
branch was clearly to be seen, lying detached in the correspon- 
ding part of the new tube. 
The cross section shown at Fig. 13 shows the newly formed 
tracheae with the connecting tunnel, and within one of the tubes 
is a section of the smaller old trachea, now floated loose in the 
balsam in which it is preserved, but which, when freshly cut, 
had its main side-branch down the side-branch of the larger tube. 
These special observations on the moult of the breathing- 
apparatus may very possiblv not bear practically on the subject of 
the prevention of warble injurv ; but they are of interest to show 
how minutely we are acquainted with the history of this maggot, 
the ravages of which are, in many cases to this day, left un- 
checked, as being a pest of unknown nature, and of which, there- 
fore, the cure is unknown ; and, further, the specimens give an 
unusually detailed example of the completeness of this internal 
moult. The sections having been taken so as to remove respec- 
tively some small fragments, both of the brown and the white 
structure at the junction of the spiracles with the tracheae, 
they may be accurately fitted together again, and thus form 
a whole, showing the old spiracle still bearing the old skin 
round its top raised on the new form, likewise surrounded by 
the new skin ; and, beneath, we have the corresponding old and 
new air-tubes. 
Other alterations of a very practical kind also take place at 
this time, or follow on this most important of the moults. The 
