THE DIPTERA. 55 



whilst others are more or less covered with greyish-white 

 hairs ; individuals are also often met with quite black and 

 shining, their hirsute covering having been completely 

 rubbed off. The female may be at once recognized by her 

 solid, fleshy abdomen, that of the male being inflated by two 

 great air-bladders, which cause that portion of the body to 

 appear semi-transparent when the insect is held up to the 

 light. The figure (2) is taken from a specimen of the latter 

 sex. 



Closely allied to the present insect is Coinptosia virida, 

 n.s. (Fig. 3), which can be at once distinguished by its 

 brilliant green eyes and pale grey clothing. The larva of 

 this species is a large white maggot, rather robust, and 

 possessing a small head. It inhabits the dense moss 

 grov/ing on the trunks of trees in the forest, feeding on the 

 roots of these plants, and finally forming an oval cocoon, 

 in which it changes into the pupa shown at Fig. 3b. 

 The perfect insect appears in a few weeks' time, when it 

 may be taken in similar situations to C. bicolor, but in 

 much fewer numbers. 



Family 



Sarapogon viduus (Plate VI., fig. 4, 4a larva, 4b pupa), 

 A voracious insect, frequenting all dry sand-banks and 

 pathways throughout the summer, and destroying the 

 numerous minute diptera found in those situations. These 

 unfortunate victims are drilled through the thorax by their 

 destroyer, which sucks them completely dry with its long 

 beak-like proboscis. The larva (Fig. 4a) inhabits rotten 

 wood, chiefly feeding upon the moist, powdery portions. It 

 is usually somewhat sluggish, but when disturbed hops 

 about with electrical rapidity. The head is very minute, 

 and the elongate body consists of twenty segments, a 

 number very unusual among larvae, the normal number 

 being twelve exclusive of the head. It lives for a con- 



