BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 27 
Methoxychlor used as a spray at a concentration of 2 percent 
proved effective for the control of sticktight fleas in two heavily 
infested poultry houses. 
Various tick insecticide formulations that might be used effectively 
and safely in dipping vats were field tested at the Kerrville, Tex., 
laboratory. Improved commercial toxaphene emulsions have been 
studied as a dip. Analyses of hair samples from cattle periodically 
dipped in the vat show that there is a gradual increase in the rate of 
toxaphene deposited on the animals. The general appearance and 
resuspension properties of the emulsion are good. Dip formulations 
of this type may prove safe for use in vats provided its use is limited 
to one season of about G months duration. Observations of wettable- 
powder dip containing sufficient BHC to give 0.025 percent of the 
gamma isomer plus 0.5 percent of DDT have continued for a year. 
Although there was a gradual decline in the concentration of the 
insecticide, the preparation provided satisfactory control of ticks, 
horn flies, and goat lice during this period. The insecticide went 
back into suspension fairly well when the dip was agitated. A com- 
mercial toxaphene wettable power dip has also been under observation 
for several months. The dip apparently gives satisfactory perform- 
ance, although the insecticide is difficult to resuspend after it settles 
in the vat. 
Injections of Insecticides Into Animals To Control Insect Pests 
A promising lead in research efforts to control bloodsucking insects 
of cattle was attained this year. Lindane was injected into cattlo 
at a rate of 50 mg. per kilogram of body weight. Mosquitoes, deer 
flies, and horn flies taking blood from injected animals were killed, 
although the results were not 100 percent perfect. In two animals 
60 to TO percent of the mosquitoes feeding were killed over an 18- and 
21-day period. 
Investigations in cooperation with the Bureau of Animal Industry 
have demonstrated that subcutaneous injections of aldrin and lindane 
in cattle at the rate of 50 mg. per kg. of body weight and dieldrin 
at the rate of 25 mg. per kg. killed most of the cattle grubs in the 
backs of cattle. A few larvae matured but failed to produce flies/ 
Further tests with systemics, conducted in cooperation with the 
Bureau of Animal Industry, demonstrated that dieldrin, aldrin, and 
lindane in peanut oil administered subcutaneously to cattle at dosages 
of 25 to 50 mg. per kg. of body weight protected cattle from screw- 
worm attack for 2 to 4 weeks. Even after the treatments lost their 
effectiveness against the larvae, flies failed to emerge from pupae de- 
veloping from matured larvae for an additional period of about 2 
weeks. Before these materials were administered to cattle, preliminary 
tests were made on guinea pigs. Further research will be required 
to determine if systemics are practical as a means of protecting 
animals from screw-worm attack. 
It should be emphasized that these chemicals are not recommended 
for use in these ways. The results obtained are important because 
this is the first demonstration that injections of chemicals will kill 
cattle grubs. Much research needs to be done to find safer and more 
effective compounds. 
