444 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19G2 



insect diseases and their use in supplementing the work of parasites 

 and predators may speed us along the road toward this goal. 



Entomologists sometimes do strange things. Not so long ago, in 

 a woodlot near Florence, S.C, at a time near midnight, on seats ar- 

 ranged as though in a theater, several scientists watched the responses 

 of male tobacco homworm moths {Protoparce sexta (Johannson)) to 

 virgin female moths confined in small cages suspended at intervals 

 throughout a much larger cage. From time to time, one or more 

 of the male moths in the large cage would become agitated and then 

 lly about one of the small cages containing a virgin female moth. 

 This was evidence that a sex attractant had been produced by the 

 female moth. The particular female inciting the male response was 

 quickly removed, the tip of its abdomen containing the recently se- 

 creted sex attractant clipped off with scissors and the abdomen tip 

 then placed in a preservative. Chemists are analyzing the attractant 

 in the hope they will be able to determine its chemical formula and 

 to synthesize it for use in programs to eradicate or control the horn- 

 worm in tobacco or tomato fields. We need to discover all possible 

 attractants for insects, for they provide means of early detection of 

 invasion by new pests, methods for measuring the effectiveness of 

 programs to eradicate incipient infestation, and they may have use- 

 fulness as direct control agents. 



Thus far, all efforts to find strong chemical sex attractants in 

 tropical fruit fly females have failed, and there are reasons for be- 

 lieving that the two sexes are brought together by fruit or vegetable 

 odors rather than by chemicals secreted by the female flies. A short- 

 range sex attractant, sounds emitted by the flies, or other unknown 

 stimuli may then induce mating. Despite the apparent absence of 

 strong natural sex attractants, tropical fruit flies are nonetheless 

 among the most responsive of all insects to chemicals. Certain com- 

 plex mixtures such as protein hydrolysates, fermenting liquids, and 

 botanical extracts are known to attract both males and females. Nu- 

 merous compounds are attractive to males only. Why there should 

 be so many more male than female lures and why the response of 

 the males to certain compounds should be so much more compelling 

 than the response of females can only be speculated upon. 



Strongest of all tropical fruit-fly lures is methyl eugenol, which 

 attracts male oriental fruit flies and is eagerly consmned by them. 

 First discovered in India more than 50 years ago, its potential use- 

 fulness was not realized until many years later when L. F. Steiner, 

 U.S. Department of Agriculture scientist, mixed this lure with a 

 poison and then impregnated the mixture on cane-fiberboard squares. 

 Wlien the squares were exposed in fruit-fly areas in Hawaii, results 

 were spectacular. Fly abundance quickly declined to such an extent 

 that the feasibility of eradication with this teclmique was suggested. 



