120, Walker, Kenneth C., Goette, Mary B., and Batchelor, Gordon S. (1954) Dichloro- 
diphenyltrichlorethane and dichlorodiphenyldichloroethane content of prepared 
meals, J. Agr. & Food Chem, 2(20): 1034-1037. 
121. Welch, Howard (1948) Tests of the toxicity to sheep and cattle of certain of the 
newer insecticides. J. Econ. Ent, 41(1): 36-39. 
122, Wingo, C. W., and Crisler, O. S. (1948) Effect of DDT on dairy cattle and milk. J. 
Econ, Ent. 41(1): 105-106. 
SYSTEMIC INSECTICIDES IN ANIMALS 
Frederick W. Plapp, Jr., William F. Chamberlain, 
and R. D, Radeleff?! 
Recent research has demonstrated the efficiency of a number of the new agricultural 
chemicals in controlling pests that affect our crops and animals. At the same time these 
findings have opened new fields of study, for knowledge as to the effectiveness of a pesti- 
cide is not enough. We must know whether it leaves any toxic residues in the crop or 
animal where it is used, Such studies must be conducted for several reasons. Aside from 
strictly a research standpoint, data must be obtainedto meet the requirements of various 
State and Federal agencies, especially those responsible for the jurisdiction of Public 
Law 518, the Miller Amendment to the Federal Food, Drug, and Cosmetic Act. 
In working with systemic insecticides, as well as with other agricultural chemicals, 
the researcher should know what happens to them, In order to measure the residues 
present, he must determine the nature of the metabolism of the insecticide within the 
animal, He must know whether the chemical is converted to other toxic materials. He 
must ascertain the nature of the detoxication processes that take place--how the insect 
and the mammal defend themselves against the insecticide. Studies on the metabolism of 
insecticides in animals are therefore aimed at finding out both what the animal does to the 
material and what the material does to the animal, 
Much of our present knowledge of the metabolism of insecticides has been gained 
through the study of compounds that show systemic activity. Utilizing techniques developed 
in conjunction with metabolism studies in animals, information has been gained as to the 
reasons why some insecticides are more toxic to certain insects than to other insects 
or to mammals. These techniques have also beenused in investigations on resistance, 
It is now known that a number of insect pests of animals can be controlled with 
systemic insecticides. Interest in this field has centered on the cattle grub, a parasite 
of major importance to the cattle industry, Estimates of the annual loss due to this 
parasite have been reported as $100 million a year (Haeussler 1952), Recent reviews 
summarized progress in cattle grub control through 1958 (Graham 1959, Peterson and 
Kingscote 1959). 
Some of the earlier research in this field was done on chlorinated hydrocarbons, 
such as DDT, lindane, and dieldrin. Some of them were found to show systemic activity 
against cattle grubs (McGregor, et al. 1955). However, it has been found that compounds 
of this class tend to be stored in fat for long periods of time and secreted in milk of 
treated animals, In recent years recommendations pertaining to their use on livestock 
and poultry have been either withdrawn or restricted, owing to the problem of residues. 
1 Entomologist, Entomology Research Division, Agricultural Research Service, U. S, Department of Agriculture, Corvallis, Oreg.; 
Entomologist, Entomology Research Division; and Veterinarianin Charge, Animal Disease and Parasite Research Division, Agricul- 
tural Research Service, U. S. Department of Agriculture, Kerrville, Tex., respectively, 
160 
