28 FLIES FOUND IN HOUSES 



This fly is usually found near houses in the early summer, 

 before the house-fly appears in great numbers. It is common 

 throughout Europe and the United States. It is not very 

 common in houses, Howard (191 1, p. 248) only finding 37 

 amongst 23,087 flies collected in dining rooms and kitchens in 

 different parts of the United States. 



Howard (p. 249) thinks "this fly is one of the dangerous 

 occasional inhabitants of houses, not only because it may breed 

 in human excreta, but because it is greatly attracted to this 

 substance when it chances to be deposited in the open." 



The full-grown laii<a is 1 1 mm. long and creamy white. " The anterior spiracular 

 processes are five lobed and are like hands from which the fingers have been amputated 

 at the first joint. The posterior spiracles are round and enclose three triangular 

 shaped areas, each containing a slit-like aperture" (Hewitt, 1910). The life-cycle 

 occupies from five to six weeks. 



The larvae live in all kinds of decaying vegetable matter 

 and also in growing vegetables. They have also been found in 

 excrement and in the remains of insects. They occasionally 

 cause intestinal myiasis in man. 



Stovioxys calcitrans. The stable fly or biting house-fly. 



This fly is grey in colour, about the size of the house-fly, and 

 is very frequently mistaken for it. It is more stoutly built, and 

 may be easily distinguished by the appearance of its proboscis, 

 which is modified into an awl-like structure, adapted for piercing 

 and sucking. In the resting position the wings are held rather 

 widely apart. It has only been included in this list because it 

 is so commonly mistaken for the house-fly, which is therefore 

 often accused of being able to bite. (PI. V, fig. 2.) 



Length. 7 mm. ; span of wings 16 mm. 



Head. The eyes in the S are separated by an area equal to one-quarter the diameter 

 of the head, and in the ? by an area equal to one-third. The frontal stripe is black, 

 and the frontal margins of the orbit and cheeks silvery white. The proboscis is 

 black and slender and projects horizontally in front of the head, being visible 

 from above when the fly is at rest. The antennse are black, and the aristae bear 

 bristles on the upper side only. 



Thorax. Dark grey, marked by four conspicuous blackish longitudinal stripes. The 

 scutellum is paler, but has a small dark transverse patch on its upper border. 

 There are many long bristles on the thorax and scutellum. 



