BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 63 
surfaces, cracks, crevices, roosts and other possible hiding places 
for common poultry mites will assure excellent control. Such treat- 
ment will also control lice on poultry. Control of the lice results from 
the vapor action of the lindane. Studies are under way to determine 
if the use of lindane as a treatment for litter in poultry houses causes 
any adverse effects on young chickens. 
Studies of Toxicological Effects of Insecticides on 
Animals Intensified 
Research studies were continued and intensified to determine the 
degree of storage of insecticides in meat and milk of beef and dairy 
cattle when insecticides are applied for external parasite control. 
The work on all phases of the project is carried out in cooperation 
with the Bureau of Animal Industry. Various commercial companies 
and the Texas and Oklahoma Agricultural Experiment Stations have 
cooperated. Beef cattle were sprayed with 0.5 percent DDT accord- 
ing to the procedure used for controlling livestock pests and sub- 
sequently fat samples were taken for analyses. A single spraying 
caused deposits of 11 to 18 p. p. m. in the fat. Two sprayings pro- 
duced 31 p. p. m. and 6 sprayings 35 p. p. m. TDE, similarly 
applied, gave about the same degree of fat contamination. Both 
insecticides were largely eliminated 6 months after the last spraying. 
A single spraying with 0.5 percent methoxychlor showed an average 
of only 2 p. p. m. fat contamination which was not increased by as 
many as 6 sprayings. Further, methoxychlor residues disappeared 
within 6 to 10 weeks after treatment. Lindane sprayed at 0.03 percent 
concentration did not produce detectable levels in the fat during 6 
applications at 3-week intervals. Cattle sprayed 36 times with 0.5 
percent DDT at 2-week intervals showed no ill effects. 
Dieldrin applied as a 0.5 percent spray to dairy cows resulted in 
excretion of as much as 7 p. p. m. of the insecticide in milk. The 
insecticide is also readily stored in fat of beef cattle when applied 
as a spray in concentrations as low as 0.05 percent. Although an 
excellent insecticide for controlling livestock pests, it probably cannot 
be recommended because of storage of the insecticide in the fat. 
Due to the urgent need for information on storage in animal fat 
of various insecticides consumed as residues on forage crops following 
treatment of various field crops for insect control, work on this 
problem was intensified during the calendar year 1951. Toxaphene 
and BHC fed to cattle and sheep at 100 p. p. m. in their diet produced 
no ill effects in a 112-day feeding period. At the end of that feeding, 
fat contamination was as follows : Toxaphene-f ed sheep, 21 p. p. m. ; 
toxaphene- fed cattle, 38 p. p. m. ; BHC-fed sheep, 117 p. p. m. ; 
BHC-fed cattle, 250 p. p. m. Experiments are under way with lower 
levels of toxaphene in the diet since treatment of forage in most 
circumstances probably would not result in residues as high as 100 
p. p. m. Aldrin and chlordane fed at 10 p. p. m. in the diet for 
112 days produced no evidence of injury but resulted in fat contamina- 
tion as follows: Aldrin-fed sheep, 55 p. p. m. : aldrin-fed cattle, 49 
p. p. m. : chlordane-fed sheep, 9 p. p. m.; chlordane-fed cattle, 11 
p. p. m. Smaller numbers of cattle and sheep were fed dieldrin, 
aldrin, and chlordane at 25 p. p. m. in the diet for 56 days. The 
animals did not orain as well as the controls. Fat contamination was 
