415 



[In reporting an experiment in which wood frog egg masses were treated with 

 DDT at the rate of 5 pounds per acre:] The experiment resulted in the liilling 

 within 3 to 5 days of all tadpoles treated with DDT. Those kept as controls or 

 treated with oil only remained alive and healthy. 



In grasshopper oU or unsalted butter fat, as little as five milligrams of DDT 

 per kilogram of fish was usually lethal to fish starved for 4 days. When given 

 in very small doses, symptoms were usually delayed 3 days or more, and death 

 was often delayed 6 to 10 days. 



It was discovered that toxicity was increased by higher water temperatures, 

 by softer water, and by low dissolved oxygen. Younger fishes were more affected 

 than the older ones. 



The investigation went on ; results of tlie work in 1946 were described 

 in Fish and Wildlife Special Scientific Report 41.^^ A third report, 

 issued in 1948 as Circular 15 of the Fish and Wildlife Service under 

 the title, "Effects of DDT and Other Insecticides on Fish and Wild- 

 life," described results of investigations conducted during 1947.-^ 



The broader implications of this kind of information were brought 

 out in several books that appeared in 1948. One was Fairfield Osborn's 

 "Our Plundered Planet" ^° which warned that "* * * the rub comes 

 when we kill without knowing enough about the aftereffects." Man 

 could not live, he declared, if all other living creatures disappeared. 



As a somewhat extreme illustration, among many others, [wrote Osborn] take 

 that form of life that man likes the least — of which the unthinking person would 

 at once .«ay. '"Kill them all." Insects. Of the extraordinary number of kinds of 

 insects on the earth — about three quarters of a million different species have 

 already been identified — a small minority are harmful to man, such as the 

 anopheles mosquito, lice, the tsetse fly, and crop-destroying insects. On the other 

 hand, innumerable kinds are beneficent and useful. Fruit trees and many crops are 

 dependent upon insect life for pollination or fertilization ; soils are cultured and 

 gain their productive qualities largely because of insect life. Human subsistence 

 would, in fact, be imperiled were there no insects." 



Later that same year, William Vogt, an agricultural expert on the 

 staff of the Pan American Union, further developed this same theme. 

 Control of insects by potent insecticides, he observed, was both neces- 

 sary and hazardous : 



Many insects, such as those which pollinate fruit trees and parasitize destruc- 

 tive insects, are extremely valuable to man, which is one reason why biologists 

 throughout the world are alarmed by the widespread and unselective use of 

 DDT. Probably less than 5 percent of the known insect species can be considered 

 a handicap to man's survival. Nevertheless, the small percentage that do attack 

 his crops and forests wreak such havoc and are so costly to control by methods 

 now known that they must be recognized as one of the most stubborn of all 

 limiting factors. Unfortunately, as modern researches have shown, current agri- 

 cult'iral methods often tend to increase damage. Furthermore, b.v his carelessness 

 or unwitting spread of pests, man has greatly increased their effectiveness.^^ 



To coj)e intelligently with the problems of environmental control, 

 Vogt contended, would require a great increase in knowledge of 

 ecology. Thus : 



The limiting factors that hold down the numbers of desirable species, from 

 nitrogen-fixing bacteria in the soil to rodent-controlling hawks, must be known 



28 U.S. Department of the Interior. Fish and Wildlife Service. DDT Investigations by the 

 Fish and Wildlife Service in 1946. Special Scientific Report 41. By Arnold L. Nelson" and 

 Eugene W. Surber (May 1947) (processed). 



29 U.S. Department of the Interior. Fish and Wildlife Service. Effects of DDT and Other 

 Insecticides on Fish and Wildlife. Summary of investigations during 1947. Circn'-Tr 1.5. 

 Bv Joseph P. Linduska and Eugene W. Surber. (Washington, U.S. Government Printing 

 Office. 1948), 19 pp. 



30 Fairfield Osborn. "Our Plundered Planet." (Boston, Little, Brown, and Co., 1948), 217 

 pp. 



» Ibid., p. 60. 



= William Vogt. "Road To Survival." (New York, William Sloane Associates, Inc., 1948), 

 p. 30. 



