8 THE NORTH AMERICAN SPECIES OF DROSOPHILA. 



The male rushes at the female, with his abdomen bent up underneath, 

 and grasps her wings with his front legs, holding them between his 

 femora and tibiae. The comb of bristles on the front femora, a second- 

 ary sexual character occurring in all the species of the genus known 

 to me, seems to be connected with this holding of the wings. The 

 female struggles when caught, and usually escapes. If she does not 

 escape immediately she soon becomes quiet, and the male attempts to 

 mate. No successful copulation has been observed, though in one 

 case a male kept hold of the wings of a female for 15 minutes and 

 repeatedly attempted to mate. 



Chymomyza procnemis: The male runs after the female, and when 

 she stops pushes her wings apart with his head, grasps them with his 

 front legs (as in C. amcena), mounts, and attempts to mate. He 

 repeatedly grasps the region of her ovipositor with his large genital 

 claspers, the abdomen being bent up underneath. Usually after 

 about a minute copulation occurs. In copula 8, 9, 18, 18 minutes. 



The forms described may be roughly classified as follows : 



1. Mounting before copulation; male holds wings of female: Chyvwmyza amcena, C. 



procnemis. 



2. No wing courtship; abdomen goes up at side: Drosophila lutzii. 



3. All wing movement in front of female; abdomen bent around at side; female spreads 



her wings : Drosophila nebulosa. 



4. Little wing-movement; female spreads her wings: Drosophila funehris, D. hydei, D. 



repleta, D. virilis. 



5. No vibration; female does not spread her wings: Scaptomyza adusia, S. gramimim, 



Drosophila caribbea, D. cardini, D. immigrans, D. robusta, D. willistoni. 



6. Vibration, circling; female does not spread her wings: Drosophila affinis, D. busckii, 



D. melanogasler , D. obscura, D. si?nulans. 

 Insufficient data: D. hypocausta, D. melanica, D. transversa. 



The members of the genus Chymomyza mount before copulation; 

 in Drosophila and Scaptomyza copulation precedes mounting. The 

 former relation is the one that appears to be usual among other Mus- 

 cidse. It occurs in the Calypterse in general, and in all the Acalypterse 

 that I have observed, belonging to the subfamilies Sepsinse, Piophilinae, 

 Trypetinse, Borborinse, and Ephydrinae. 



The final position of mated pairs is in general the same throughout 

 the group of Drosophilinse, so far as observed. The same position is 

 the rule in the rest of the Muscidse. I have observed it in many 

 Calypterae and in the acalyptrate subfamilies mentioned in the pre- 

 ceding paragraph, as well as in the Cordylurinse. It occurs in some, 

 but not in all, Syrphidse. The only exception known to me among the 

 Muscidse is in the case of the genus Lonchcea, one mated pair of which 

 I have observed. This pair was in the end-to-end position; but 

 that may not be the normal process for the species (apparently L. 

 polita Say) . 



