i6o Arthropods as Simple Carriers of Disease 



Hodge (19 lo) has approached the problem of fly extermination 

 from another viewpoint. He beheves that it is practical to trap 

 flies out of doors during the preoviposition period, when they are 

 sexually immature, and to destroy such numbers of them that the 

 comparatively few which survive will not be able to lay eggs in suffi- 

 cent numbers to make the next generation a nuisance. To the end 

 of capturing them in enormous numbers he has devised traps to be 

 fitted over garbage cans, into stable windows, and connected with the 

 kitchen window screens. Under some conditions this method of 

 attack has proved very satisfactory. 



One of the most important measures for preventing the spread 

 of disease by flies is the abolition of the common box privy. In 

 villages and rural districts this is today almost the only type to be 

 found. It is the chief factor in the spread of typhoid and other 

 intestinal diseases, as well as intestinal parasites. Open and ex- 

 posed to myriads of flies which not only breed there but which feed 

 upon the excrement, they furnish ideal conditions for spreading con- 

 tamination. Even where efforts are made to cover the contents 

 with dust, or ashes, or lime, flies may continue to breed unchecked. 

 Stiles and Gardner have shown that house-flies buried in a screened 

 stand-pipe forty-eight inches under sterile sand came to the surface. 

 Other flies of undetermined species struggled up through seventy- 

 two inches of sand. 



So great is the menace of the ordinary box privy that a number of 

 inexpensive and simple sanitary privies have been designed for use 

 where there are not modem sewer systems. Stiles and Ltimsden 

 (191 1) have given minute directions for the construction of one of the 

 best types, and their bulletin should be obtained by those interested. 



Another precaution which is of fundamental importance in 

 preventing the spread of typhoid, is that of disinfecting all discharges 

 from patients suffering with the disease. For this purpose, quick- 

 lime is the cheapest and is wholly satisfactory. In chamber vessels 

 it should be used in a quantity equal to that of the discharge to be 

 treated. It should be allowed to act for two hours. Air-slaked 

 lime is of no value whatever. Chloride of lime, carboHc acid, or 

 formalin may be used, but are more expensive. Other intestinal 

 diseases demand similar precautions. 



Stomoxys calcitrans, the stable-fly— It is a popular behef that 

 house-flies bite more viciously just before a rain. As a matter of 



