NEW DATA AND SPECIES IN SIMUUlDiE 179 



the last three jomts all black. Hind legs with the femur yellow, black- 

 ened toward apex ; tibia mostly black, the base and an incomplete broad 

 ring before middle pale ; tarsi with the first joint whitish, its apical third 

 and the lower margin blackened, the second joint white basally, black on 

 apical half, third joint narrowly pale at base, the last two joints wholly 

 black. Claws with a stout tooth near base. Wings hyaline, the vena- 

 tion normal ; thick veins ferruginous yellow ; no iridescent spot in anal 

 field. Halteres pcJe yellow, infuscated at base. 



Length : Body about 3 mm., wing 4 mm. 



Cordoba, Mexico, December 1 7, 1907, one female (F. Knab); Las 

 Vegas Hot Springs, New Mexico, August 7, one female (H. S. Barber). 



Type, Cat. No. 19112, U. S. Nat. Mus. 



The reddish shade of tlie mesonotum is not strong and is further 

 obscured by the strong gray pruinosity ; in certain lights the ground-color 

 appears very dark and the markings described above as black stand out 

 strongly white-pruinose. The specimen taken in December at Cordoba 

 was no doubt a straggler out of season. 



The species just described agrees closely in coloration, size, and struc- 

 ture with Simulium ruhrithorax Lutz, which occurs in southern Brazil 

 and of which two females are before me, kindly transmitted by Dr. Lutz. 

 This latter species has the terminal joint of the antennae longer and more 

 tapered ; the frons is slightly narrower and almost parallel-sided ; the hairs 

 on the frons are coarser amd disposed in four rows, of which the outer 

 ones are very obvious. In ruhicundulum the hairs of the frons are finer 

 and scattered over the surface without the least tendency to form rows. 

 Another case of vicarious closely similar species, that of Simulium esco- 

 meli and 5. bivittatum, has already been pointed out (Proc. Biol. Soc. 

 Wash., xxvii, 1914, p. 83). 



Simulium trivittatum Malloch. 



Simulium distinctum Malloch, Proc. Enl. Soc. Wash., xv, 133 (1913). 

 Simulium trivittatum Malloch, Tech. Ser. 26, Bur. Ent.. 29. 30 (1914). 

 SimuUum distinctum MaUoch, Tech. Ser. 26, Bur. Ent., 25, 29. 30 (1914). 



Examination of the type material described under distinctum and tri- 

 vittatum leaves no room for doubt that the two are conspecific. The 

 type of trivittatum (female) and the two female paratypes of distinctum 

 agree in every detail. Contrary to what is indicated in Technical BuUe- 

 tin 26, page 29, the abdomen of the type specimen of trivittatum is 

 most distinctly marked, showing three series of black spots on a pale 



