CHEMOTEOPTC TESTS WITH THE SCREW-WORM FLY 25 
MIXED NITRO COMPOUNDS 
Picric acid, and chloropicrin in lubricating oil in dilutions of 1 in 
10 and 1 in 25, are very effective repellents during five days' exposure. 
Chloropicrin in dilutions of 1 in 50 and 1 in 100 of lubricating oil are 
effective over the first and second days of exposure. Although the 
number of screw-worm flies available at the time the tests with 
para-nitroaniline were made was very small and no generalization 
can be made, this compound does not look promising for use as a 
repellent. 
Picric acid is not of value in preventing infestation, but chloro- 
picrin in dilutions of 1 in 10 and 1 in 25 of lubricating oil prevented 
all infestation and emergence. 
AMINES 
Dimethylaniline, both undiluted and in combination with petro- 
latum and kaolin, is a good repellent for the first two days of exposure 
only. One test with alpha-naphthylamine indicates that it has 
good repellent value over the entire five-day period. 
Dimethylaniline is of little value in preventing infestation after 
the first day of exposure. The jar treated with alpha-naphthylamine 
was not infested till the fourth day. No Cochliomyia emerged from 
meat treated with any of the amines. 
MISCELLANEOUS NITROGENOUS COMPOUNDS 
Pyridine is a very good repellent against screw-worm flies, and 
although all 10 jars were infested by the third day, there was no 
emergence of Cochlioruyia. 
Nicotine sulphate is of no value either as a repellent or in prevent- 
ing infestation. 
SULPHUR COMPOUNDS 
EthyLmercaptan is one of the most strongly attractive compounds 
to screw- worm flies tested. The results with allyl isothiocyanate 
are not consistent; when diluted with either mineral oil, petrolatum, 
or kaolin it appears a stronger repellent than when undiluted. An 
interesting contrast between the action of compounds very similar in 
chemical constitution is shown by ethyl and butyl mercaptans. The 
ethyl compound is strongly attractive to the flies, the meat treated 
with it is infested as soon as the untreated meat, and Cochliomyia 
emerged from both of the two jars treated with it. On the other 
hand, butyl mercaptan is a pretty good repellent for the first two 
days of exposure, and though all the jars were infested on the second 
day, there was no emergence of Cochliomyia. There was no emer- 
gence of Cochliomyia from meat treated with allyl isothiocyanate, 
either. 
SELENIUM COMPOUNDS 
The data on these compounds are too few for generalization, but 
are indicative that the selenium compounds are repellent for the first 
day of exposure only, and have no action on infestation. 
