FLIES FOUND IN HOUSES I9 



habits of F. cajticularis , F. scalaris, and L. ccesar are of special 

 importance, and are more fully dealt with. In the case of 

 M. domestica special chapters are devoted to the life-history 

 and to the anatomy and habits of the adult. 



It has been thought desirable to give, in later chapters, 

 detailed descriptions of certain important species of foreign flies 

 which cause myiasis or apparently spread disease, since it is 

 difficult for observers to consult communications in journals and 

 reports of societies. 



Musca domestica L. The common house-fly. 

 The general colour is mouse grey. (PI. II, fig. i.) 



Length. 6 — 7 mm.; span of wings 13 — 15 mm. 



Head. In S the eyes are separated by an area equal to one-fifth to one-fourth the 

 width of the head, and in ¥ by an area equal to one-third. Frontal stripe dark 

 velvety brown in S , velvety black with reddish tinge, narrow below and very 

 broad above in ? . Frontal margin of eye white in S , almost obliterated by 

 frontal stripe in ? . Cheeks and face silky white to yellow, 'shot' with brown. 

 Antennce brown ; aristae black and feathered. Palps black. 



Thorax. Grey, marked by four equally broad dark longitudinal stripes, most clearly 

 defined in front. Scutellum grey with blackish sides. Some long bristles on 

 sides of thorax and scutellum. 



Wings. Clear, but yellowish at base. The end of the 4th longitudinal vein bent 

 sharply upwards so as nearly to meet the vein above it. Squamae large, opaque, 

 yellowish. Halteres yellow and covered by squamae. 



Legs. Blackish brown. 



Abdomen. The sides of the basal half in S , and frequently in 9 , ochraceous buff, 

 and somewhat transparent. The posterior segments brownish grey, with yellowish 

 shimmer, and bearing a few slender bristles. A longitudinal brown band usually 

 occupies the centre of the anterior segments. Looked at from the dorsal surface 

 apparently four segments are visible. In reality the visible segments are five in 

 number, but the first can only be detected with difficulty owing to its being much 

 reduced in size and fused with the second. In the ? the long ovipositor formed 

 by the posterior segments may sometimes be seen, but is usually telescoped in the 

 abdomen. 



Mjisca domestica is probably the most widely distributed 

 insect to be found ; the animal most commonly associated with 

 man, whom it appears to have followed over the entire earth. 

 It extends from the sub-polar regions to the tropics, where it 

 occurs in enormous numbers. 



