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in the current of air outside the window, it will be found that 

 the males have no difficulty in locating her. The instant 

 that one passes to the leeward, he turns in his flight and 

 begins M'orking against the wand directly toward her. I have 

 also observed that if a female alights upon the ground and then 

 flies away, males will congregate for a short time around the 

 spot where she had been. They show the greatest agitation, 

 fluttering around, and grasping at different objects with their 

 claspers. 



From these facts it would appear that the female attracts the 

 male by a volatile exhalation, and that this, acting on the nerves 

 of the male, produces sexual desire, and prompts him to fly 

 against the wind. 



That this volatile exhalation is principally from the ovipositor 

 is evident from the fact that this organ is only distended at those 

 times when the males are active and the females willing. It is 

 not distended to facilitate copulation, for the instant that the 

 female feels the slightest touch from the approaching male it is 

 withdrawn, the horny ring surrounding its base is protruded, 

 the abdomen contracts and becomes rigid, particularly on the 

 ventral surface, thus drawing the genitals downward and foi- 

 Avard ; then she is ready for copulation. That the exhalation is 

 not wholly from the ovipositor would appear from the fact that 

 sterile females, three or four days old, in whom this organ is 

 dried and shrunken, and only protruded for the purpose of laying 

 eggs, still have the attractive power. They resist every ap- 

 proach of the males, beating them off' with their wings, and 

 struggling to escape, but, if held fast in the fingers, the males 

 will succeed in copulating. These females are unable to fly 

 any great distance, in fact are quite abortive, and in the natural 

 •order of things would not exist. 



The experiments of Mr. Trouvelot have proved that the 

 antenna? of the male are necessary for the recognition of the 

 female. Observation wmII show in what manner. When he is 

 not in a state of repose, his antennas are in constant vibration, 

 movino; back and forth in the direction of their broadest faces. 

 This motion is very noticeable as he hovers just to the leeward 

 of the female that he is approaching. This vibration of the 



