when fly production is at a rate of several billion a year. The Honolulu, Hawaii, and 

 Mexico City tropical fruit fly laboratories of the Entomology Research Division, 

 currently under the direction of L. F. Steiner and W. E. Stone, respectively, have made 

 outstanding progress in developing procedures for rearing these insects by the millions 

 or billions at a cost ranging from about $100 to $200 per million. Workers in other 

 countries including Costa Rica, Israel, Greece, and Egypt are also making important 

 contributions to mass-rearing procedures for tropical fruit flies. 



The tobacco insects research laboratory of the Entomology Research Division, at 

 Oxford, N.C. , under the direction of F. R. Lawson, has made excellent progress in 

 developing mass -production procedures for the tobacco homworm (Protoparce sexta 

 (Johannson)) that probably would fall within a cost range of $5,000 to $10,000 per million 

 moths. Certain insects, such as Drosophila fruit flies, certain mosquitoes, the house 

 fly (Musca domestica L.), the face fly (Musca autumnalis De Geer), and perhaps many 

 crop pests could be mass-produced at costs that probably would be substantially less than 

 $100 per million. 



Investigators with the Entomology Research Division and cooperating State experi- 

 ment stations have made excellent progress in the development of rearing methods for 

 the production of virtually unlimited numbers of such insects as the pink bollworm 

 (Pectinophora gossypiella (Saunders)), the boll weevil, codling moth (Carpocapsa 

 pomonella (L.)), the European corn borer ( Ostrinia nubilalis (Hiibner)), the cabbage 

 looper ( Trichoplusia ni (Hiibner)), the corn earworm (Heliothis zea (Boddie)), and other 

 species that, even as late as 5 to 10 years ago, were regarded as difficult to rear imder 

 laboratory conditions. Basic studies on insect nutrition by Erma S. Vanderzant of the 

 Division's cooperative cotton insects research laboratory at College Station, Tex. , have 

 contributed much to the progress on mass-rearing methods for a wide range of crop 

 insects. 



Necessity for Appraising Natural Population Density 



With the possible exception of concern over mass-rearing procedures, the writer 

 has gained the impression that most entomologists regard high natural population 

 densities as the chief obstacle to successful application of the sterile-insects-release 

 method. This is among the most vital of the factors to be considered in appraising the 

 potential merits of the method. The dearth of quantitative information on natural insect 

 population densities per unit area is really appalling. Information on actual numbers per 

 acre, per square mile, per individual host tree, or any other unit of measure applicable 

 to the pest involved, is absolutely necessary in order to make a reasonable approxima- 

 tion of the merits, or lack or merit, of the sterile-insects-release method. It is the 

 writer's view that there is a general tendency for entomologists to overestimate the 

 natural population density during periods of scarcity of the species. When precise 

 information is lacking, and entomologists are asked to estimate the natural population 

 density of the insects they are investigating, they tend to think of the situation when the 



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