34 THE MAGGOT OF 



The body of the maggot (Fig. i) consists of 13 segments, 

 including the head. Limbs are totally absent, and locomotion is 

 effected by the muscular contractions of the body, aided by a zone 

 of sharp recurved points, with which every segment is provided. 

 The integument of insects consists of two layers : an external 

 structureless membrane or cuticle, and an internal cellular 

 epithelium. In the latter may be distinguished an external 

 pigmentary layer, where the cells are rendered angular by mutual 

 pressure, and to which the colouration and hardness of the 

 integument is due, and a soft internal layer of spheroidal and 

 nucleated cells. With the exception of the recurved points just 

 alluded to, where a certain amount of colouration and induration is 

 present, the skin of the maggot presents only the inner soft layer, 

 the cells of which, measuring roughly 1-5 00th of an inch in 

 diameter, are represented in Fig. 2. 



The integument is reflected inwards at the mouth and at the 

 anus to form the alimentary canal, which has also two coats — an 

 outer membranous, and an inner cellular one. It is difficult, 

 however, to regard them both as continuous with those of the 

 external integument, since that which is external in the one is 

 obviously internal in the other, and vice versa (see Fig. 3). 

 After passing through the pharynx, an organ to be presently 

 described, the oesophagus divides into two branches, one of which 

 shortly enters the crop, a large oval sac (^., Fig. 4), which may 

 generally be seen by its dark colour, through the integument of 

 the dorsal surface of the larva. It forms a reservoir for the food 

 before its passage into the stomach, and is usually filled with dark 

 brown contents. In Ta?typJis,'^ it will be recollected, the crop is a 

 simple enlargement of the canal preceding the proventriculus. Here, 

 however, the enlargement seems to have taken place on one side 

 so as to form a deep pouch or sac. That the walls of this sac are 

 muscular is evidenced by an hour-glass constriction which oc- 

 casionally passes down them, keeping the contents in motion. 

 The other branch of the oesophagus, after passing through the 

 great nerve-centres of the insect, enters the proventriculus, which is 

 a globular chamber with thick cellular walls, formed by a reflection 

 of the oesophagus upon itself, the termination of the latter, hanging 



* See this Journal, vol. i, p. 83. 



