388 MEDICAL ENTOMOLOGY 



.The hind-gut presents an equally striking peculiarity, in that it is shut 

 off from communication with the mid-gut and also from the exterior, and 

 thus serves only as a receptacle for the secretion of the Malpighian tubes. 

 It commences at the termination of the wide tubular third portion of the 

 mid-gut, at which point it is shut off from the cavity in front of it by a 

 tight constriction, and passes upwards on the dorsal surface of the sac, 

 turning again downwards to end at the anus, immediately internal to 

 which there is a second constriction. The four Malpighian tubes, which 

 are arranged in two pairs, one of each pair being shorter than the other, 

 enter the hind-gut immediately behind the first constriction. It is note- 

 worthy that there are no salivary glands in the larva. 



Immediately after birth the larva crawls away to find a suitable place 

 for pupation. It progresses actively by means of wave-like contractions 



of the body wall upon the fluid contents, and can under- 

 Pupation 



go, in the passage of any obstacle, very remarkable 



changes in shape ; on occasion the anterior part of the body is dis- 

 tended and used as a battering ram. In a very short time the larva finds 

 some crevice or hollow, a slight fissure in the earth, or a clump of dead 

 leaves or debris, which will afford it some shelter, and comes to rest, 

 usually at a depth of an inch or so beneath the surface. Pupation then 

 takes place without further movement, and within a half or three-quarters 

 of an hour the change is completed. The pupariiim (Plate XLVI, 

 fig. 12) resembles in general that of most Muscids, being oval in shape, 

 and slightly broader in front than behind ; at the' posterior end there 

 are the conspicuous caudal protuberances, the shape of which, and of 

 the notch between them, afford a valuable means of distinguishing 

 puparia belonging to different species (Austen). The puparium, when 

 fully formed, is of a dark brown colour, and measures 6'5 mm. in length 

 and 3*5 mm. in breadth. 



Bagshawe, who was the first to find the puparia in nature, obtained 

 them on the shore of a lake, usually about ten yards from the water, and 

 not more than twenty-five yards away. They were lying from half an 

 inch to a little more than an inch below the surface, in the shelter of ban- 

 ana plants, shrub, and undergrowth, and always in a dry and crumbling 

 soil ; they were sometimes found in crevices of rocks and at the roots of 

 trees. Comparative dryness seems to be a favourable condition for them, 

 and most of the localities in which they were found were such that rain 

 water would be quickly drained off. 



Fraser and Marshall found immense numbers of puparia on the main 

 Islands of Sesse in Lake Nyanza, in dry sand on the shore about five to 



