4 BULLETIN 1472, U. S. DEPARTMENT OP AGRICULTURE 
materials, and contain only incidental information on the toxicity of 
these materials to the eggs, larvae, or adults. 
From a practical point of view there are a number of factors which 
must be considered. Among these are availability of the materials, 
their cost, adhesive qualities, suitability for handling, stability or 
keeping qualities, whether they stain wool or mohair, and the effect 
on the animal tissues, which has already been mentioned. Some 
may feel that the value of a repellent for use on living animals can 
not be determined by tests conducted with dead tissue. It seemed 
to the writers, however, that a determination of the reaction of flies 
toward a large number of materials, exposed under observable con- 
ditions, would give, with a minimum expenditure of time and money, 
the basic information upon which to proceed with other studies. 
This assumption is being justified by work now in progress. The 
various practical points mentioned above will be considered in con- 
nection with a subsequent report on the treatment of livestock and 
other uses to which repellents are commonly put. Some of the 
results of field tests with repellents have been presented. 6 
There are many other uses to which repellents may be put. For 
instance, there is considerable loss from the infestation of foods by 
flies, aside from the danger of disease being conveyed to man through 
eating foods contaminated by them. Throughout the South, and 
even in the cooler parts of the country, it is often difficult to dress 
meat on the farm or range or even in well-equipped slaughter houses 
without having it " blown" by flies. Slaughtering at night, the use 
of smudges, and other means of avoiding this are practiced, but with 
only partial success, whereas a good repellent would largely solve the 
difficulty. Again, tourists and picnic parties are often greatly 
annoyed and their foods contaminated so as to render life outside of 
screened houses well-nigh unbearable. The use of an effective 
repellent under such conditions has been found of great value. Such 
repellents would serve a useful purpose about the household, dairy, 
and all establishments where foods are handled or displayed. 
Another, though somewhat different, phase of this subject is the 
use of repellents to protect livestock of all classes from annoyance 
by flies, especially the blood-sucking forms, such as the horn fly, 
stable fly, and buffalo gnat. Although this particular series of experi- 
ments does not consider, directly, this use of repellents, it is thought 
that the information gained will aid materially in this field; in fact, 
the data have already furnished valuable clues which are being 
followed in the work now under way with sprays for flies on livestock. 
This bulletin presents. the results of jar tests with the screw-worm 
fly, CocMiomyia macellaria Fab. The results of the tests with the 
house fly, Musca domestica L., the green bottle flies, Lucilia spp., and 
other species will be presented in subsequent papers. 
MATERIALS TRIED 
As very few observations on the chemotropic responses of blow- 
flies to various chemicals have been recorded heretofore, the materials 
used in these tests were selected from a wide range of organic and 
inorganic compounds in order to reconnoiter the whole field of possible 
6 Laake, E. W., Parman, D. C, Bishopp, F. C, and Roark, R. C. field tests with repellents 
FOR THE SCREW-WORM FLY, COCHLIOMYIA MACELLARIA FAB., UPON DOMESTIC ANIMALS. Jour. Econ. Ent. 19: 
636-539. 1926. 
