20 THE BLOWFLIES oF NortH AMERICA 
economical method of reducing the hazard of fecal-borne epi- 
demics on construction jobs. 
'Sewage-treatment plants sometimes attract blowflies by their 
odors and the flies so attracted may feed upon partly or poorly 
digested sludge. Modern and properly administered treatment 
plants are not a breeding source of such flies. 
Disposal of dead animals. Many species of blowflies breed in 
bodies of dead animals. Dead stock on ranches or dead men on 
battlefields are sources of great swarms of these flies. The control 
of blowflies under such circumstances depend on proper poison- 
ing with sodium arsenite or carcass disposal. Large carcasses 
will produce the greater numbers of blowflies, other things being 
equal, but the common practice of throwing bodies of small 
animals upon manure heaps, into weed patches, or behind barns 
will result in the development of considerable numbers of these 
flies. Bodies of very small animals such as rats, mice, or birds 
may produce many blowflies during various stages of careass 
decay and at certain seasons of the year. Rodent-control units 
often prove to be very successful in killing great numbers of rats 
or other rodents by baiting and fumigating but few such units 
make an attempt to incinerate or otherwise dispose of resulting 
dead animals. These may cause the spread of epidemies of plague 
or other rodent-borne diseases such as typhus. Burial of animals 
is a satisfactory means of disposal if the body is buried suffi- 
ciently deep to prohibit access to the careass by ovipositing blow- 
flies. Incineration of animals is considered more satisfactory if 
carried to completion. Any animal suspected of having died from 
an infectious disease should be burned. Under any circumstance, 
burning, burying, or treatment by sodium arsenite or benzene 
hexachloride spray, must be accomplished as soon as the dead 
man or animal is found. Dead men on battlefields are usually 
buried. Large carcasses of animals are most easily burned in a 
trench dug as long as the animal, slightly narrower than the 
width of the animal’s body and from 12 to 18 inches in depth. 
Less physical effort is required to dig such a trench beside the 
animal than to drag the careass to the trench. When the trench 
has been dug and filled with wood, the carcass is rolled over on 
it, and the wood is fired at the windward end of the trench. 
An incinerator prepared in this manner will satisfactorily dis- 
pose of a medium-sized carcass within a few hours. Any remains 
may be buried in the trench when it is refilled. 
CONTROL OF ADULT BLOWFLIES. Blowflies some- 
times occur in considerable numbers in well-cared-for areas, 
and a reduction in their abundance may be desirable. This is 
