238 INSECTS AND MAN 



distinct from most dipterous larvae. The pupa is of the 

 usual brown colour and barrel shape. 



The blow fly or blue-bottle, Calliphora erythrocephala, 

 cannot be mistaken for the house flies already mentioned ; 

 its larger size, its dark blue colour, and its rapid, noisy 

 flight render it a most conspicuous insect. On occasion, 

 oviposition may take place in excrement and decaying 

 vegetable matter, but it is on meat that the eggs are 

 usually laid. The females are exceedingly prolific, as 

 many as six hundred eggs being deposited by a single fly. 

 In from eight to twenty hours the larvae, commonly called 

 gentles, emerge ; they may be distinguished from those of 

 the house fly by their larger size and by the twelve 

 tubercles on the posterior end. In a little over a week the 

 pupal stage is reached, and it usually lasts a fortnight. 



The stable fly, Stomoxys calcitrans (fig. 32), is very 

 closely related to, and often confused with, the house fly. 

 A moment's examination with a lens will reveal the fact 

 that this fly is armed with an awl-like proboscis, which 

 usually projects straight forward from beneath its head, 

 whereas the house fly has a soft sucking proboscis. There 

 are other differences, of course, but, as the stable fly is 

 described elsewhere, we need not enumerate them here. 

 This insect is only an occasional visitor to houses ; it is a 

 lover of the sun and open air, and, as its popular name 

 implies, it is usually found in propinquity to horses and 

 cattle. 



Muscina stabulans, as we have mentioned, is called the 

 stable fly in America, though the name is a misnomer, 

 for the fly is not a frequenter of stables. Like Fannia 

 canicularis, it is active in the early summer, and in appear- 

 ance it resembles a large house fly. It is a vegetable feeder, 

 and lays its eggs in rotting animal or vegetable matter. 



Two other flies found in houses, from time to time, are 

 the latrine fly, Fannia scalaris, and the cluster fly, Pollenia 

 rudis. The former closely resembles the lesser house fly, 



