BEHAVIOR OF THE FRUIT FLY 227 



Why should enormous numbers of male fruit flies and only 

 a few females be captured in certain oils? Concerning the be- 

 havior of Dacus zonatus towards citronella oil, Howlett (1, 

 page 413) writes: ' Since the -reaction was confined to the 

 male sex and did not appear to be in any way connected with 

 feeding habits, it seemed most reasonable to suppose that the 

 smell might resemble some sexual odour of the female which 

 in natural conditions served to guide the male to her." This 

 is, in substance, a view which we also expressed to a number 

 of entomologists and mentioned in a paper read before the Agri- 

 cultural Seminar in Honolulu on January 11, 1912, to explain 

 the behavior of the male Mediterranean fruit fly towards kero- 

 sene. Howlett believes that "the smell is in all probability 

 perceived by means of the antennae," for, after he had carefully 

 amputated these "at the base of the second joint," none of the 

 mutilated insects were attracted to the oil of citronella. 



If it is true that kerosene gives off an odor which resembles 

 that emitted by the female fruit flies to attract the opposite 

 sex, then how would the fact be explained that a few females 

 are usually caught in the oil? We would have to assume that 

 the specialized sense organs present in the males to locate the 

 females are absent in the latter. We would then be forced to 

 conclude that the females were not attracted to the kerosene, 

 but came within the sphere of influence of the oil by accident, 

 became stupified and dropped into the oil. There is, of course, 

 the possibility that the reaction of the male Mediterranean 

 fruit fly towards some volatile part of the petroleum oils may 

 be a positive chemotaxis "not representing the sexual smell 

 of the female," a possibility to which Howlett also calls atten- 

 tion in the behavior of Dacus zonatus toward citronella oil. 



BIBLIOGRAPHY 



1. Howlett, F. H. The Effect of Oil of Citronella on Two Species of Dacus. 



1912. Trans. Ent. Soc. London, pt. II, pp. 412-8. 



2. Weinland, H. A. The Present Fruit Fly Situation and some Results of the 



1912. Hawaiian Campaign. Cat. State Comm. Hort., Mon. Bull. I, No. 

 11, pp. t45-852. 



