U4 The Common House Fly. [Sess. 



The fly is a very old friend. Probably they made their 

 first appearance during the formation of the tertiary rocks, as 

 fossils of flies occur in them. We often see flies embedded in 

 the fossil resins known as amber. 



Natural History. — The common house fly got its scientific 

 name from Linnaeus in 1761, when he called it Musca 

 domcstica. There are many other flies found in dwelling- 

 houses along with the house fly, but they never exist in 

 anything like the same number, and even a slight examination 

 will show how greatly they differ from it. 



The lesser house fly (Fannia canicidaris) is often thought 

 to be a young fly not fully grown. This of course is not 

 true, as when a fly emerges from its pupa case it is fully 

 grown. The lesser house fly is of a lighter colour and more 

 delicately built. It also appears earlier in the year and 

 prolongs its stay later than the common fly. Under excep- 

 tional conditions, however, the domestic fly may be smaller 

 than normal, and this is probably due to unfavourable con- 

 ditions during its larval stage — e.g., insufficiency of food or too 

 great dryness of the foodstuff. 



Another fly, the Stomoxys calcitrans, may also be mistaken 

 for the house fly, and then it is erroneously concluded that 

 the common fly has bitten one, when in reality it is the awl- 

 like proboscis of the stomoxys which has caused the injury. 



The house fly belongs to the group Muscidae, which is 

 one of the sub-orders of the Diptera or two- winged flies. The 

 body, £-inch long, is composed of head, thorax, and abdomen. 

 The remarkably mobile head is connected with the thorax by 

 a very slender neck, and carries the maxillary palps and the 

 proboscis. The upper part and sides of the head consist 

 mainly of the large compound eyes. In the case of the males, 

 the eyes are set closely together, and wider apart in the 

 female. In addition to the compound eyes, the fly possesses 

 three simple eyes or ocelli, set in triangular form on the 

 crown of the head. The antennae, which act as organs of 

 touch and probably smell, are placed between the eyes, and 

 each consists of three segments. The fly has four black lines 

 on the back of its thorax, the bristles of the antennae are 

 feathered, and the vein which ends near the tip of the wing 

 is distinctly elbowed. The whole surface of the fly is more 



