446 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



A significant step forward was the discovery, again by L. F. Steiner 

 in Hawaii, that deposits from a bait spray containing protein 

 hydrolysates and a mild phosphatic toxin such as mahithion attract 

 tropical fruit flies and are consumed avidly by them, with ensuing 

 fatal stomach-poison action. Only small amounts of actual toxicant 

 per acre are needed for control. The knowledge that protein hydroly- 

 sates contain elements essential to the development of sexual maturity 

 and fecundity of fruit flies was the discovery of Dr. Kenneth S. 

 Hagen, a University of California Agricultural Experiment Station 

 scientist. Amazingly successful, this new protein hydrolysate bait 

 spray has been used to eradicate one extensive Mediterranean fruit fly 

 infestation and appears to have eluninated another in Florida. A 

 similar bait spray is being used to prevent establislmient of the Mexi- 

 can fruit fly in southern California. Research conducted by J. G. 

 Shaw, another U.S. Department of Agriculture scientist working in 

 Mexico, proved the bait spray to be effective against this fniit fly. 

 The same bait spray, sometimes modified, is now known to be effective 

 against a number of tropical and temperate-zone fruit flies in other 

 parts of the world. 



Few could have guessed years ago that knowledge of the nutritional 

 requirements of tropical fruit flies obtained by Dr. Hagen would lead 

 to a safe control method that could be applied by air over cities and 

 towns as well as on crops. 



If 10 pairs of normal insects are placed in a cage and 100 males that 

 have been sterilized by exposure to gamma radiation from a cobalt '^^ 

 source are then added, there will be a strong decrease in the fertility 

 of eggs laid by the normal females. If sterile males continue to be 

 added at the same high, overflooding ratio at frequent intervals, 

 fewer and fewer normal females may be produced in each subsequent 

 generation. Soon the entire population may be extinguished. This 

 exciting noninsecticidal method of insect control was conceived by 

 E. F. KJnipling, director of U.S. Department of Agriculture's 

 Entomology Research Division, and first successfully used on the 

 screw- worm fly {Gallitroga hominivorax (Coquerel)), a serious pest 

 infesting wounds of cattle.^ The method requires the rearing and 

 sterilization of large numbers of insects and their later distribution 

 throughout the area inhabited by the pest. The new technique has 

 eradicated the screw-worm fly throughout Florida and other South- 

 eastern States with savings to the cattle industiy of about $20 million 

 each year. The fly-rearing and sterilization f actoiy used in this first 

 large-scale operation of the sterilization principle cost about $1 million 

 and had a capacity of 50 million sterile flies per week. The fleet of 



1 See article entitled "Screwworm Eradication : Concepts and Research Leading to the 

 Sterile-Male Method," by E. F. Knipling, in the Annual Report of the Smithsonian Instl- 

 tultlon for 1958, pp. 409-418. 



