PREVENTIVE MEASURES 
205 
extent. Confining ourselves strictly to the fly question 
and to no other, an earth closet unprovided with a 
removable bucket and from which the contents are re¬ 
moved only at considerable intervals is little better than 
the uncared-for privy, except that it is usually less ac¬ 
cessible to flies. A slight covering of earth over the 
contents is no protection against the emergence of 
adult flies coming from larvae within the substance. 
It is not a protection against infestation from flies 
coming in from outside, since these have been shown 
to lay their eggs upon the earth covering excreta. 
When the eggs hatch, the young larvae, being very ac¬ 
tive, soon burrow to their proper food. 
Accurate experiments have been made by several 
observers concerning the distance which the newly 
emerged fly will struggle through earth to the air. 
Hine (in lit.) experimented with ordinary soil and 
found in a single experiment that adults were not able 
to emerge from a depth of six inches, but Stiles and 
Gardner, of the U. S. Public Health and Marine-Hos¬ 
pital Service, have shown that, -in experiments with 
sterilized sand, house flies to the number of thirty- 
seven, issuing from fecal material buried in a screened 
standpipe under forty-eight inches of sand, came to 
the surface. Some of these flies were sent to the 
writer’s office for determination and were named by 
Mr. Coquillett. They were in a somewhat damaged 
condition, due probably to their long struggle for free¬ 
dom. In the same series of experiments, other flies of 
undetermined genus and species struggled up to free- 
