DESCRIPTION OF THE MAGGOT. 



vn 



changes, as above mentioned, to a more pear-shaped form, placed 

 with the smallest end (containing the minute horny spiracles at its tip) 

 uppermost, and thus with the compact hard-tipped apparatus above, 

 and the growing body behind, is well calculated to force open and 

 enlarge the passage down which it came. 



The size and shape of the perforation through the hide altered 

 progressively with the growth of the maggot. At first this passage 

 was very little larger at the lower than at the upper opening; and, 

 though the walls of the perforation had now become smooth and 

 shiny, I could not distinguish the presence of any distinct lining 

 membrane. With the enlargement of the passage its shape became 

 more cone-like (corresponding with the altering form of its tenant) ; 

 and, on March 5th, I found for the first time a distinct pellicle or skin- 

 like membrane covering the walls of the perforation, or passage, and 

 continuous with the lining of the maggot-cell below. 



The great change, both in the appearance and the internal structure 

 of the maggot, took place when it was grown to about a third of its 

 full size, when it assumed its well-known 

 shape. Previously to this, whilst the work 

 of forming its passage was still in progress, 

 its chief characteristics externally were the 

 absence of everything that could obstruct 

 its power of pressing onwards ; and inter- 

 nally it was little more than a bag of fluid, 

 with a large proportion of the space occupied 

 by breathinfj -tubes, — a very important con- 

 sideration relatively to available methods 

 of destroying the creature. At the period, 

 however, of its moult to its final stage a 

 change takes place respectively in the nature, 

 or in the amount, of development of nearly 

 the whole of both the internal and external structure of the maggot. 

 The hard tips necessary, or at least serviceable, for forcing a passage 

 up the hide, are no longer needed, and they are exchanged for a broad 

 form of spiracle (fig. 8, p. 8), and the internal organs become suited 

 to provide material for the development of the fly, which will pre- 

 sently form in the dry husk of the maggot which serves as the 

 chrysalis-case. 



In methods of destruction of warble-maggot a large proportion turn on 

 choking up their breathing-apparatus. This consists mainly of two 

 large breathing-tubes, or trachea;, which draw in air at the tip of the 

 tail by two perforated bodies known as spiracles (see fig. 5). 



From the earliest stages which I had opportunity of observing up 

 to date of change mentioned in preceding paragraph the general form 



Fig. 5. — Breathing-tubes of 

 maggot, magnified. 



