ENTOMOLOGY AND I'l.ANT QUARANTINE 
67 
Studies oil the life history and habits of the Gulf coast tick, one of the most 
serious predisposing causes of screwworm attack in the Southeast, have 
indicated practical methods of controlling this species of tick. 
To study the screwworm problem and develop practical control measures 
under range conditions the Bureau has established a ranch experiment station 
at Menard, Tex., comprising some 1,200 acres and using approximately 900 
sheep, goats, and cattle as experimental animals. 
CATTLE GRUBS 
Experiments with solutions of rotenone have yielded a simple and efficient 
method for reducing the abundance of cattle grubs. A solution composed of 
50 cc of benzol, 5 cc of cresol, 45 cc of liquid petrolatum, and 1 g of rotenone 
was found to be as efficient when applied to the surface of the skin and 
rubbed with the fingers as when the solution was injected into the opening 
of the lesions individually. The survival of grubs from such general applica- 
tions ranged from 1.25 to 7.69 percent. When this method is used, from three 
to five times as many cattle can be treated by one operator as when the 
solution is injected into the lesions individually. The method is particularly 
suited to the treatment of dairy cattle and provides a cheap, quick remedy 
against the losses to the dairy industry occasioned by these pests. 
A histological study of the migrations of the larvae in the host have cor- 
roborated earlier findings resulting from gross examination. The investiga- 
tions also showed that the esophagi invaded by the cattle grub exhibited an 
extensive inflammatory edema, which was confined mainly to the outer layers 
and was composed principally of a hematogenous exudate, with eosinophils, 
plasmocytes, and lymphocytes predominating. Infiltrating fluids caused dis- 
tortion and injury resulting in an apparent weakening of the walls of the 
esophagus. 
CATTLE AND HORSE LICE 
In experiments on the control of lice on cattle and horses where the use of a 
dipping vat is not feasible, as is often the case during the winter months, 
the powdered roots of derris and devil's shoestring have been found efficient 
and economical because of their effectivenes.? even when greatly diluted. 
I>erris root containing 3 percent of rotenone was effective for both iDiting and 
sucking lice when diluted to 0.125 i)ercent rotenone by mixture with diatoma- 
ceous earth in the ratio of 1 part to 23 parts of the diluent by weight. Powdered 
devil's shoestring diluted to the same concentration of rotenone was equally 
effective. 
It was found also that a solution of 0.5 g of rotenone in 100 cc of carbon 
tetrachloride, when sprayed lightly into the coat of an animal with an ordinary 
hand sprayer, is a very prompt and effective treatment. The carbon tetra- 
chloride evaporates almost instantly, leaving the fine particles of rotenone in the 
hair. While this preparation is more easily and more rapidly applied than 
the powders, the materials are more costly, since about 4 fluid ounces of the 
solution was required to treat a full-grown animal. 
GOAT LICE 
Following the experimental work of the Bureau which demonstrated the 
effectiveness of 325-mesh wettable sulphur for the control of lice of sheep and 
goats, many ranchmen in certain parts of the Southwest are enthusiastically 
employing this material for ridding their flocks of these parasites. The 
treatment is reported to increase the mohair production approximately one- 
fourth pound per animal. In order to make the sulphur usable as a dip with 
all kinds of water, over 400 tests have been made to determine the best 
wetting agent to be u.sed in connection with the sulphur in alkaline waters. 
These tests have determined that at least six combinations of neutral .sodium 
oleate with sulphonated-alkylated diphenyl. a sulphonic acid of an aromatic 
hydrocarbon, and a sodium salt of alkyl ester of sulphosuccinic acid are suit- 
able as wetting agents in water rendered alkaline by the presence of sodium 
or magnesium salts. 
FLY SPRAYS AND REPELLENTS 
In investigations in the development of more efficient fly sprays and repel- 
lents, especially for use on livestock and in barns, a biological method of assay- 
ing the in.secticidal value of fly sprays has been perfected in which u.se is 
made of an accurately regulated mechanism governing the air stream, dosage. 
