".*? I*''* *''* :** ; * /NEMT YORK STATE MUSEUM 



It will probably be impracticable for some years to come to keep 

 dwellings entirely free from insects, yet it is feasible to prevent 

 pests becoming uncomfortably numerous in houses and in the 

 vicinity of dwellings and to make it nearly impossible for insects to 

 gain access to disease germs and thus serve as carriers of dangerous 

 infections. 



FLIES 



There are a number of flies which occur in houses, about build- 

 ings, stables and camps. The house fly is the most important and 

 frequently comprises about 98 per cent of those found in dwellings. 

 The cluster fly and various meat or blow flies are the insects usu- 

 ally seen in houses during the winter or early spring. The house 

 fly appears comparatively late. Each species of fly has its peculiar 

 habits, which must be taken into account in any serious attempt to 

 solve the fly problem, though broadly speaking conditions favorable 

 or unfavorable to the breeding of one species of fly are very apt to 

 have a corresponding effect upon other species. Flies are active, 

 with keen senses, and consequently readily find attractive food or 

 breeding conditions even at considerable distances. For example, 

 Bishopp in lit. states that he succeeded under rural conditions in 

 recovering a considerable number of house flies and several species 

 of blow flies at distances of 5 miles from the point of liberation. 

 Exact knowledge of the preferences or the behavior of flies is 

 essential to successful control. 



The effect of environment upon flies was shown by the fact that 

 from 800,000 to 500,000,000 aerobic bacteria to a fly were found 

 on insects taken in either insanitary or congested city areas, while 

 the number for those captured in the more sanitary or less-con- 

 gested suburban districts ranged from 21,000 to 100,000. It was 

 also found that flies caught in milk shops apparently carry more 

 bacteria than those from other stores handling exposed food in 

 similar neighborhoods. The reason is probably because milk, when 

 accessible during the summer months, is a suitable culture medium 

 for bacteria, and the flies first inoculate the milk, later reinoculate 

 themselves, and then more of the milk, thus establishing a vicious 

 circle. 1 



House flies, blow flies and flesh flies are the more prevalent 

 species about packing houses and abattoirs. The common black 

 blow fly, Phormia regina, is the most troublesome, and is 

 often supplemented in the middle of the season by green flies, 



1 Cox, Lewis & Glynn. Jour. Hyg., 12:290-319. 1912. 



