352 A. H. STURTEVANT 



of the work was done at the Cold Spring Harbor Laboratory in 

 the summer of 1911, and I wish to express my appreciation of 

 the interest in the experiment shown by Dr. C. B. Davenport 

 at that time. 



COURTSHIP AND MATING 



Most of my observations on courtship in Drosophila have 

 been made upon D. ampelophila Loew. In general the process 

 is very similar in D. busckii Coq., but differs in several respects 

 in D. amoena Loew, D. repleta Woll., and D. funebris Fabr. 

 The first and most noticeable act in courtship occurs when 

 the male, being near the female, extends one wing at about 

 right angles to his body, and vibrates it for a few seconds. The 

 wing is then returned to the normal position and the process 

 is repeated, usually with the other wing. But between times 

 there is a scissors-like movement of the wings repeated several 

 times. This vibrating of the wings is often repeated many 

 times, and may be done in any position relative to the female, 

 though the male a 1 ways faces her. Usually, in fact, he swings 

 quickly around her in a semicircle once or oftener during the 

 process. Soon the male begins to protrude his genitalia and, 

 if the female remains quiet, to lick her posterior end. Some 

 white matter now protrudes from her ovipositor, and other males 

 in the same vial are usually 'observed to become excited now 

 and begin courting; indicating odor as a cause of sexual excite- 

 ment. If the female runs or flies away the male is excited, moves 

 his wings jerkily, and walks around rapidly, but seems unable 

 to follow the female accurately or to locate her quickly. The 

 ' penis is directed forward by bending up the abdomen under- 

 neath, towards the thorax, and is jerked toward the female 

 (the male always standing facing her at this stage), but not 

 always toward her genitalia, as I have seen ii strike her in the 

 eye. 2 If it does strike the mark the male mounts on the female's 

 back, between her wings. Mounting never takes place until 

 after the actual copulation has occurred, in which respect Droso- 

 phila differs from some related flies (e.g., Muscidae, Anthomyidae, 

 Sepsidae, Borboridae, and Ephydridae, so far as my observa- 

 tions go). In these forms the male flies and lights on the female, 



2 The male in this case, however, had white eyes, and so was perhaps blind, 

 Normally the aim is accurate. 



