t) PROCEEDINGS OF THE NATIONAL MUSEUM vol.69 



Distribution. — British Columbia : Kalso, July 5, 11, 1903 (H. G. 

 Dyar). 



California: Seneca, Plumas County, June 1, 1923 

 (V.S.Barber). 



Idaho : Gospel Mountain, July 12, 1907 (J. M. Aid- 

 rich). 



Montana : Two Medicine Lake, July 4, 1921 (H. G. 

 Dyar). Belton, June 19, 1921 (H. G. Dyar). 



Washington : Kitsap Lake, Bremerton, April 29, 

 1924 (H. G. Dyar). Hoodsport, May 3, 1924 

 (H. G. Dyar). 



PROSIMULIUM MAGNUM, new species 



The largest species in our fauna. 



Female. — Closely allied to hirtipes but may be easily separated by 

 its unusually robust appearance ; two basal antennal joints yellowish, 

 remainder dark: three basal antennal joints enlarged, remainder 

 tapering to a point; fore tarsi more elongate, the basitarsus di=!tinctly 

 larger than antenna ; stem vein pale pilose. Ovipositor : Much larger 

 and stronger than hirtipes, reaching the tips of the last segment 

 which are drawn out to equal the blunt cerci and strongly hairy. 

 (Figs. 1 and 2.) 



Male. — Essentially as in hirtipes. The spines on the claspers are 

 much stronger and more widely separated than the hirtipes from the 

 same locality (Figs. 22 and 23.) 



Larvae and pupae were found by the junior author, April 12, 

 J 925, in Dead Run, Va., a small stream that descends among recks 

 the sharp decline of the banks of the Potomac. The pupae project 

 from an irregular, rather dense web on a leaf or stone where the 

 water is swift, and are often densely crowded together. The pupal 

 filaments are multiple-branched about 10 trunks, at the base of each 

 tuft, which fork near the base, some fork a second or even a third 

 time, the total number being 30-40. 



Type locality. — Dead Run, Fairfax County, Va., from reared 

 material. 



Type. — Male, allotype female, paratypes 3 males, 2 females, Cat. 

 No. 28326, U.S.N.M. ^ 



Fourteen specimens at hand. 



Distribution. — Maryland: Plummers Island, April 19, 1903; 

 April 28, 1909 (E. A. Schwarz, ^V. L. McAfee). 

 Cabin John, April 28, 1912 (J. R. Malloch). 

 Michigan: Grand Ledge, Aprir28, 1912 (H. G. 



Hubbard). 

 Virginia: Great Falls,, April 24, 28, 1915 (R. C. 

 Shannon). Dead Run, April 32, 1925, April 19, 

 1914 (R. C. Shannon), 



