22 BULLETIN 1472, U. S. DEPABTMENT OF AGKICULTUKE 
DISCUSSION OF RESULTS 
COMPOUNDS 
HYDROCARBONS 
Petrolatum is the only hydrocarbon exhibiting a decided repellent 
action, and this persists during the first day of exposure only. How- 
ever, since 1,636 flies out of the total number of 1,659 visited one 
of the six jars, and 1,454 of these appeared on the second day, it 
is possible that the meat in this jar was incompletely covered with 
the petrolatum, and that additional tests will show petrolatum to 
have a repellent action persisting during the entire time of exposure. 
The tests with lubricating oil, toluene mixed with petrolatum, 
naphthalene, and anthracene were made at times when the number 
of screw-worm flies present was insufficient to yield an accurate 
result. 
The hydrocarbons are not effective in preventing infestation. 
The best from this standpoint is toluene, since only two out of six 
jars treated with this compound were infested. 
BROMIDES 
Para-xylyl bromide is one of the strongest repellents against 
screw- worm flies discovered in the course of this investigation, its 
coefficient of attractiveness being only 0.16. Its repellent action 
persists during five days of exposure. Although it seemingly loses 
its repellent action when mixed with lubricating oil, these tests were 
made when too few flies were available for drawing a conclusion. 
Alpha-bromonaphthalene also is a good repellent against Cochliomyia 
flies, and its action persists for at least three days. The tests with 
bromoform mixed with kaolin, ethylene bromide, and benzyl bromide 
were made at times when the number of screw-worm flies present 
was insufficient to yield an accurate result. 
Para-xylyl bromide is very effective in preventing infestation. 
None of the meat treated with the pure compound was infested 
with any species of fly, and none of the meat treated with para-xylyl 
bromide in lubricating oil, either in 1 per cent or 10 per cent solution, 
hatched out Cochliomyia flies. Alpha-bromonaphthalene prevented 
infestation of meat till the third day of exposure, and no Cochlio- 
myia emerged from any of the jars treated with it. 
CHLORIDES 
A single test with chloroform indicates that it is attractive to 
screw-worm flies. Pinene hydrochloride and benzyl chloride are the 
most strongly repellent of the chlorides tested and are effective over 
the entire period of five days' exposure. Hexachloroethane is 
effective over a period of three days. Para-xylyl chloride is very 
much less effective than the corresponding bromide. The tests 
with benzyl chloride mixed with lubricating oil, para-xylyl chloride 
mixed with lubricating oil, and chlorinated naphthalene are incon- 
clusive, owing to the absence of an adequate number of flies at the 
times the tests were carried out. 
Benzyl chloride and benzyl chloride in lubricating oil were effective 
in preventing infestation by any species of fly, and para-xylyl chloride 
