4 THE HOUSE FLY DISEASE CARRIER 



ble it, the house fly can be distinguished by having no 

 bristles on the sides of the thorax above the attach- 

 ment of the last pair of legs and by having the vein 

 that ends near the tip of the wing distinctly elbowed, 

 a short distance before its apex. Several different 

 kinds of Tachinidae, Dexidae and Sarcophagidre have 

 a superficial resemblance to the house fly, and, like it, 

 have the elbowed vein, but all of them differ from the 

 house fly in possessing a row of bristles above the 

 point of attachment of the last pair of legs. The only 

 other family containing species that might be mis- 

 taken for the house fly is the Anthomyidae, but none 

 of these has an elbowed vein. 



"In the foregoing paragraph I stated that the house 

 fly can be distinguished from nearly all of the other 

 kinds of flies that resemble it by the two characters 

 mentioned. We have, in this country, a species agree- 

 ing with it even in regard to the two characters given. 

 Indeed the resemblance is so close that only an ex- 

 amination under a lens or microscope will reveal the 

 principal difference existing between these two spe- 

 cies. I refer to Musca autiujiualis DeGeer.* In the 

 male of this form the eyes are in contact on the upper 

 part of the head, whereas in the male of the house fly 

 the eyes are widely separated and the black stripe be- 

 tween them is of nearly the same width throughout its 

 length. In the female of autvmnalis the dark stripe 

 between the eyes is only as wide as the added breadth 

 of the narrowest part of the two gray stripes which 



*The Musca corvina Fabricius, 1781. 



