160 Arthropods as Simple Carriers of Disease 
Hodge (1910) has approached the problem of fly extermination 
from another viewpoint. He believes 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 Lumsden 
(1911) 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, carbolic 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 belief that 
house-flies bite more viciously just before a rain. As a matter of 
