NEW SPECIES OF TWO-WINGED FLIES FROM WESTERN 

 NORTH AMERICA BELONGING TO THE FAMILY 

 TIPULIDAE. 



By Charles P. Alexander, 



Of the Massachusetts Agricultural College, Aviherst. 



The new species described in this paper were included in very 

 extensive collections made in Alaska by Dr. J. M. Aldrich, and in 

 Western United States, British Columbia and Alaska, by Dr. Harrison 

 G. Dyar. The two collections taken together, which belong to the 

 United States National Museum, constitute one of the most impor- 

 tant series of these flies that has yet been brought together from this 

 region. In the present paper a part of the undescribed forms are 

 included. It is hoped that detailed records of all the included spe- 

 cies can be brought together and published in a second report on 

 these flies. All types have been deposited in the collection of the 

 United States National Museum. 



ORMOSIA DECUSSATA, new species. 



Allied to 0. longicornis (Doane) ; antennae of male elongate, the 

 flagellar segments attenuated; general coloration of mesonotum 

 brown, the pleural region pale reddish grey; wings with the stigma 

 and costal region pale brown; cell 1st Mg open; anal veins conver- 

 gent; male hypopygium with the outer angles of the gonapophyses 

 produced into elongate, curved spines that are feebly decussate at 

 their extreme tips. 



Male. — Length about 4.5 mm.; wing, 5.7 mm. 



Rostrum and palpi dark brown. Antennae of the male elongate, 

 brown, a little shorter than the body, the flagellar segments attenu- 

 ated apically. Head greyish brown. 



Mesonotum pale greyish brown, the humeral region of the praescu- 

 tum obscure yellow. Pleura pale reddish grey, the dorso-pleural 

 region more yellowish, Halteres obscure yellow, the knobs darker. 

 Legs Avith the coxae and trochanters yellow; remainder of the legs 

 brownish yellow, the terminal tarsal segments dark brown. Wings 

 with a pale grey suffusion the stigma and the costal and subcostal 

 cells brownish; veins brown. Venation: r at fork of Rs+s] basal 



No. 2500. — Proceedings U. S. National Museum. Vol. 64, Art. 10. 



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