SYSTEMATIC ACCOUNT. 97 



Wings slightly yellowish, veins brown. Costal index about 4.6; fourth-vein index about 

 1.3; 5x index about 0.9; 4c index about 0.7. 

 Length body 3 mm.; wing 3.2 mm. 



Specimens examined: Ottawa, Canada (W. H. Harrington); Franconia 

 (Mrs. Slosson), Hanover (C. W. Johnson), Bretton Woods (C. W. Johnson), 

 New Hampshire; Chester, Massachusetts (C. W. Johnson); Ithaca, New 

 York (R. C. Shannon); Pottstown, North Mountain, Pennsylvania (C. W. 

 Johnson); Cabin John Bridge (types), Linnieville, Maryland (R. C. 

 Shannon); District of Columbia (U. S, Nat. Mus. coll.); Dead Run, 

 Glencarlyn, Virginia (R. C. Shannon); Georgia (U. S. Nat. Mus. coll.). 



Drosophila virilis Sturtevant. 1916. Aim. Ent. See. America, 9, -330. 



cf , 9 . Arista with about five branches above and two below. Antennse brown, third 

 joint dark opaque reddish-brown. Front over one-third width of head, wider above; dull 

 coffee-brown, ocellar dot black. Second orbital one-third other two. Second oral bristle 

 three-quarters length of first. Only one long bristle on each palpus. Carina broad, shghtly 

 sulcate, nosehke; face somewhat shiny, brown. Cheeks yellowish brown; their greatest 

 width over one-fourth greatest diameter of eyes. Eyes pUose. 



Acrostichal hairs in six rows; no prescutellars. Mesonotum and scutellum dark dull- 

 brown. Pleur£B and abdomen dull brown, somewhat darker. Legs pale brown. Apical 

 and preapical bristles on first and second tibiae, preapicals on third. 



Wings clear, veins brown. Costal index about 2.8; fourth- vein index about 1.8; 5x 

 index about 1.2; 4c index abolit 0.9. 



Length body 2.8 mm.; wing 3.0 mm. 



Specimens examined: New York, New York (types); Terre Haute, 

 Indiana (R. R. Hyde). I have also one specimen, collected at St. Elmo, 

 near Chattanooga, Tennessee (W. S. Adkins), that may belong here. The 

 specimen is badly damaged, but agrees with this species so far as can be 

 seen, except that the carina is not at all sulcate. It does not agree with 

 any other species known to me. The New York record rests on a single 

 pair bred from a pineapple exposed at Columbia University, in November 

 1913, and descendants of this pair. This stock is still being kept in large 

 numlDers by Dr. C. W. Metz, who has used it 

 extensively in genetic experiments. The Terre 

 Haute record rests on one series taken by Dr. 

 R. R. Hyde in a grocery store, and likewise 

 kept as a stock. I have seen living material 

 of this strain. It is identical with the New 

 York stock. The species is very hardy and 

 easily kept in the laboratory. This fact makes 

 its great rarity in nature surprising. The fact 

 that both of the certain records are based on 

 material collected about buildings suggests 

 that the species may be an introduced one. 

 It may well have been described under an- 

 other name from some other region, though 

 I have been unable to find any description Fig. 48.— Drosophila virilis. 

 with which it can be identified. Head. 



The eggs have four filaments. The females 

 ordinarily do not begin to lay until they are four or five days old. About 

 three weeks are required for development. The mating habits, chromo- 

 somes, and genetic experiments dealing with this species are described else- 

 where in this paper. 



The small eyes and broad cheeks (fig. 48) make this species obviously 

 distinct from such types as D. robusta (fig. 6) that resemble it superficially. 



