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NliW YORK SIATI': Mrsi-.iNr 



Flight and dissemination. 'Jhis is sonicthiiii^ of great import- 

 ance in view of the part Hies may play in the spread of disease. The 

 experiments of Dr L. O. Howard, Government hjitomologist, have 

 shown conclusively that the major portion of ll:e tiics about a 

 buiUHng breed in the immediate vicinity, jjrohably within 300 to 

 5CK) feet. There is no denying the fact that this insect is capable 

 of flying considerable distances but ordinarily this does not seem 

 to occur. There is another phase of this question which has ap- 

 parently received little consideration, namely, the conveyance of 

 flies l)y vehicles of one kind or another. Only a little observation 

 is necessary to show that the butcher cart of tlie country is a very 

 efficient carrier of flies, presumably receiving accessions and leav- 

 ing individuals at almost every stopjiing place, even though the 

 route traversed may occupy an entire day. The same is true, 

 though to a more limited extent, of trolley cars and express cars 



carrying sacked meat or other supplie-^ 

 eciually attractive to flies. It is onl_\ 

 necessary for these carriers to load 

 where conditions are favorable for the 

 infection of flies and we may have a 

 mysterious outbreak of disease at some 

 distance from the source of trouble. 



Natural enemies. The house fly, 

 though so abundant, is subject to attack 

 by various natural enemies. One of the 

 most common is a fungous disease 

 known as E m p u s a m u s c a e which 

 is occasionally responsible for the death 

 of many flies, particularly toward the 

 end of the summer. It is not uncom- 

 mon to find a few individuals affected 

 by this disease every year. A small, 

 reddish mite may be occasionally found 

 attached to flies, seriously weakening 

 the host. There are, in addition, wasps 

 and spiders which prey upon flies and 

 undoubtedly are of considerable service 

 Fig. 12 ?iouse centipede; seen thousfh tlicv are Very rarch'' sufficiently 



from above, enlarged, the head o - j ^ 



still mire enlarged. (After Wood) abundant to materially rcducc the num- 

 bers of this pest. Another interesting enemy of the house fly 

 is known as the house centipede, Scutigera forceps Raf., 



