32 BULLETIN 1472, U. S. DEPARTMENT OF AGRICULTURE 
animals, the chemotropic responses of three species of blowflies (the 
screw-worm fly, Cochliomyia macettaria Fab.; the green-bottle fly, 
Lucilia sericata Meig.; and the black blowfly, PJiormia regina Meig.), 
and the house fly (Musca domestica L.) to a wide range of organic and 
inorganic compounds, essential oils, plant products, and pine-distilla- 
tion products have been determined. 
The repellent or attractant action of 353 compounds and mixtures 
upon the screw-worm fly, CocJiliomyia macellaria Fab., is reported in 
this bulletin. 
The chemotropic effect of these materials was tested by smearing 
5 cubic centimeters of the liquids or 5 grams of the solids over 4 
ounces of fresh beef liver contained in a pint Mason jar. These jars 
were then exposed in the proximity of a packing house or other envi- 
ronment where flies were abundant. Tests were made at Dallas and 
Uvalde, Tex., during the summer months. Untreated meat was 
exposed at the same time, and the chemotropic effect of the materials 
is calculated by the ratio of the number of flies visiting the treated 
jar over the number of flies visiting the untreated or check jar. A 
total of 1,152 treated jars are reported in this bulletin. 
About 20 of the organic compounds diminish the normal attractive- 
ness of beef liver to Cochliomyia flies from 100 to 10 or less. These 
are representative of nine different classes of organic compounds. 
Four of these compounds are naphthalene derivatives, and seven 
others are characterized by causing intense irritation to the eyes of 
man, and were used during the World War as "tear gases." There 
are not sufficient data on the organic compounds to show clearly any 
consistent relation between chemical constitution and repellent value. 
There appears to be no relation whatever between the repellent action 
of the organic compounds tested and their boiling points. 
Only one inorganic compound, copper carbonate, is an effective 
repellent for screw-worm flies. A number of the essential oils are 
good repellents, among which are Ceylon citronella oil and American 
pennyroyal oil, commonly used as mosquito repellents. Powdered 
pyrethrum and derris, both of which are valuable contact insecticides, 
are effective in repelling screw- worm flies. 
Except for the conclusion presented in the following paragraph, no 
attempt is made to draw conclusions as to the practicability of utiliz- 
ing on livestock the substances tested. The results herein presented 
serve as a basis for tests on living animals, which are now under way. 
Furthermore, it is felt that these studies are a step in the direction of 
obtaining a better insight into the fundamental principles underlying 
the chemotropic responses of insects. 
Of all the materials tested as repellents against the screw-worm 
fly, certain products obtained from the pine are among the best. 
These include pine oil, both the destructively and steam distilled, 
crude turpentine, pine tar, and pine-tar oil. In view of the cheapness, 
availability, nontoxicity, and adhesiveness of pine-tar oil, the writers 
are of the opinion that this is the best material among all of those 
tested to use upon wounds of domestic animals to protect them against 
the screw- worm fly. 
U.S. GOVERNMENT PRINTING OFFICE 
