92 



THE NORTH AMERICAN SPECIES OF DROSOPHILA. 



Australia, Hawaii, or Europe, in all of which regions D. melanogaster is 

 apparently common. 



In life this species can be seen to be a little darker than D. melanogaster 

 and a little stouter in shape. These differences are, however, not obvious 

 unless a large series of each is examined. The eggs are quite different 

 (see plate 1). 



The genetic experiments with this species and its hybrids with D. melano- 

 gaster are described elsewhere in this paper (pp. 14 and 117). 



Head of Male. 



Fig. 45. — Drosophila melanogaster. 



Fig. 46. — Drosophila simulans. 



Since this species has not been distinguished from D. ynela nog aster, but is 

 now common in the Eastern States in the same situations as that species, 

 the same arguments as were applied to D. melanogaster may be shown to 

 indicate that D. simulans is also an introduced form. -Since it has not been 

 recognized except from the United States, Central America, and Brazil, 

 it seems very probable that it was brought in from the American tropics. 

 The date of introduction was probably rather recent; of the specimens 

 examined from this country the one from Key Largo is the only one col- 

 lected before 1913, and that one was only a year or two earlier. Quacken- 

 bush (1910) was probably dealing with this species, in crosses with D. 

 melanogaster. His material was collected at Woods Hole, Massachusetts, 

 in 1908. 



Drosophila caribbea Sturtevant. 1916. Ann. Ent. Soc. America, 9, 335. 



cf', 9. Arista with about five branches above and three below. Antennae yellow, 

 third joint brownish. Front nearly one-half width of head, wider above; reddish yellow. 

 Second orbital about one-third other two. First oral bristle one and one-half times second. 

 Carina rather broad, flat. Face, cheeks, and proboscis yellow. Greatest width of cheeks 

 less than one-sixth greatest diameter of eyes. Eyes with thickly set, short pile. 



Acrostichal hairs in eight rows; no prescutellars, although there is a transverse row of 

 slightly enlarged hairs between the posterior pair of dorsocentrals. Mesonotum, scutellum, 

 and pleurae dull pale brownish-yellow. Legs pale yellow. Apical and preapical bristles on 

 first and second tibise, preapicals on third. 



Abdomen brownish yellow, each segment with an indistinct brownish posterior margin. 



Wings clear. Costal index about 1.5; fourth-vein index about 2.4; 5x index about 2.0; 

 4c index about 1.6. 



Length body 2 mm.; wing 2.2 mm. 



