Sept., I9I4-] Severin-Severin : Mediterranean Fruit Fly. 247 



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 certain oils give 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 oils ? We should 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 petroleum oils, but came within the sphere of influence 

 of the oil by accident, became stupefied 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 attention in 

 the behavior of Dacus sonatiis towards citronella oil. 



The behavior of the Mediterranean fruit flies was occasionally ob- 

 served in the neighborhood of the traps. In some instances, fruit flies 

 remained at rest on the inside of the pans for long periods of time as 

 if stupefied by the volatile parts of the oil. In other cases, the flies 

 would walk along the inside of the pan for a time, then take wing 

 and fly up to a neighboring leaf or twig, or in their apparently dizzy, 

 zigzag flight over the surface of the petroleum oils they would plunge 

 into the oil and generally cease all activity noticeable to the naked eye 

 in less than half a minute. 



It certainly is peculiar that the male Mediterranean fruit flies 

 plunge into the petroleum oils to their own destruction. The flies 

 may be attracted to the oil as a result of a chemotaxis due to one or 

 more hydrocarbons or to the impurities of the petroleum oils, such as 

 the sulphur constituents or nitrogenous prodvicts. Small quantities of 

 sulphides are detected by the human nose and it may be possible that 

 the minutest traces are perceived by the fruit flies. Furthermore, 

 sulphides have recently been found within the bodies of insects. 

 Again, the hydro-carbons of the oil may act as an anesthetic, and 

 stupefy the insects whenever they remain within their influence. It 

 is known that the volatile parts of gasoline, for instance, have a 

 stupefying effect upon animals. According to a scientist connected 

 with the Standard Oil Company, cases are on record where men, who 



