lO 



FLIES FOUND IN HOUSES 



antennae and the upper margin of the mouth is the face ; that 

 behind and below the eye is the cheek^. 



In most of the flies here described each antenna consists 

 of three dissimilar segments, the terminal one being much 

 produced ventrally and bearing far back on its true upper 

 surface a bristle or arista, which may be bare, or furnished with 

 hairs variously arranged. 



The thorax, or middle division of the body, consists of three 

 segments firmly united together and carries the single pair of 

 zvings, the Jialtcres, and the three pairs of legs. The dark lines 

 running through the wings and forming the supporting frame- 

 work of the wing-membrane, are termed veins or nerviires and 

 the areas between them cells. The main veins run longitudinally 



humeral vein 



subcostal cell 



1"^ Long it. vein 



costal ve/n 



Fig. 4. Right wing of house-fly {M. doinestica). 



from the base to the tip of the wing, but there are also some 

 cross veins, three being placed in the central part of the wing, 

 one very short the others longer, which are clearly shown in the 

 accompanying illustration, in which the small cross vein is seen 

 to be about in the centre of the wing. The differences in the 

 arrangements of the veins afford ready means of distinguishing 

 the common house frequenting species. On the hind margin of 

 the wing, near the base, there is often a more or less free lobe 

 called the alula. Internal to the posterior lobule of the wing 

 there are often placed one or two smaller membranous plates, 

 known as the squama and antisquania. " The squama is thicker 

 than the rest of the wing and is attached posteriorly to the 



1 Wingate (1906, p. 10) calls "the parts below the cheeks and the eyes," Xhtjou'ls. 



