1919] Sfurferant — Species Closely Resembling Drnsophila melanogaster 153 



A NEW SPECIES CLOSELY RESEMBLING DROSOPHILA 

 MELANOGASTER. 



By a. H. Sturtevant, 

 Columbia University, New York City. 



In the course of genetic experiments with Drosophila melanogaster 

 Meigen a wild race was found that gave unexpected results. Ex- 

 amination showed that it was structurally different from typical 

 D. melanogaster. The new form has been found to be common and 

 widely distributed. Since it is evidently a distinct species that has 

 hitherto been overlooked, and since it will certainly be extensively 

 discussed in genetic literature in the future, the following name and 

 descrijjtion are presented. 



Drosophila simulans, sp. nov. 



Closely similar to D. melanogaster Meigen in size, color, shape, 

 venation, chaetotaxy, and in the presence of tarsal combs in the 

 male. The eyes are a little larger and the cheeks a little narrower 

 than in that species; but these differences are not sufficiently well- 

 marked to serve as diagnostic characters. The external male 

 genitalia, shown in figure 2, are clearly distinct from those of D. 

 melanogaster (figure 1) : The most reliable differences here are in 

 the size and shape of the posterior process (p) of the large anterior 

 plate, and in the shape and vestiture of the smaller comb-bearing 

 plate (c). In relaxed pinned material the two species may be 

 separated by means of the posterior process. In D. melanogaster it 

 appears as a small hook; in D. simulans it resembles a clamshell, 

 since the basal part is not usually observable. 



Living material shows several other slight differences, not definite 

 enough to serve for purposes of classification, but observable in 

 large series as average differences. D. simulans has a slightly 

 darker mesonotum, often with a bubble beneath the surface in the 

 mid-dorsal line. The abdomen is a little stouter, the wings a little 

 shorter. The dark abdominal bands of the female are not quite as 

 deep black as those of D. melanogaster. The egg has two filaments 

 at its anterior end, that are somewhat longer, and less dilated at 

 their tips, than those of D. melanogaster . 



Type, allotype, and gonotypes: bred, in New York City, from 



