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). 

Heap or MALE. 
Fria. 45.—Drosophila melanogaster. Fig. 46.—Drosophila simulans. 
Since this species has not been distinguished from D. melanogaster, 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. 
o, . Arista with about five branches above and three below. Antenne 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 pleurz dull pale brownish-yellow. Legs pale yellow. Apical and preapical bristles on 
first and second tibix, 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. 
