AMERICAN DIPTERA. 343 



black ; head and thorax subopaque gray pruiuose. Third joint of the antenn^ 

 oval, onlT slightly longer than the, second. Wings grayish hyahne, the costal 

 portion h'evond the base of the suhmarginal cell extending from the co^ta to the 

 fourth vein brown, the limits not sharply defined, second basal cell shgh y 

 shorter than the first, anal cell wholly wanting. Front femora only shghtly 

 thicker than the others. 3-4 mm. 



Behring Island (Stejniger). 



Tachy«lroinia corticalis sp. nov. 

 Male Length 3.5 mm.-Black species covered with fine brown gray dust. 

 Occiput grayish, with a few black bristles above and numerous white hairs be- 

 low • front brownish. Antennae yellow at the base, the outer joint and its seta 

 infu'scated. Proboscis reddish, with the tip darkened ; palpi white, with a strong 

 black preapical hair. Thoracic notum covered with brown-gray dust, the large 

 humeri, the pleura and scutelhim with more cinereous dust, scutellum with two 

 erect widelv separated bristles. Abdomen flattened, hypopygium large shining 

 black, globose, the copulatory portion twisted to the right, asymmetrical, consist- 

 ing mainlv of two large lamellate pointed valves, the one on the right with a 

 bunch of short black hairs on its upper side, clasping a complicated short central 

 piece bearing a short fringe of forward extending hairs, the last ventral is pro- 

 vided with a series of long black hairs. Coxa, and legs shining, piceous, front 

 ones li-hter, the four anterior femora swollen, of nearly equal thickness, front 

 femoral narmed, ornate with two circular black spots on inner side below, one 

 at the middle, the other half-way towards the apex ; front tibia slightly thicker 

 than the middle ones, armed beneath with a series of equidistant black setula, 

 front metatarsi also with minute setula below; base of middle femoi-a with a 

 rou-h pencil of black bristles fitting into the excised tip of the middle tibia, 

 mid'dle tibia in length equalling their femora, provided with close minute setu- 

 laon the under side; hind legs slender, their knees, middle part of tibia and 

 base of metatarsi dull yellowish. Halteres dirty white. Wings and veins black- 

 ish on outer two-thirds, basal third whitish, anal vein vanishing at its tip, much 

 recurved, the distance between the central cross-veins slightly less than the 

 length of one of them, anterior cross-vein rather oblique, posterior cross-vein per- 

 pendicular. 



Two males; Cloudcroft, New Mexico, June 19, 1902. 



Mr. Viereck took these specimens, together with a series of 

 Tachydromia rapax, running up and down the smooth trunks of 

 the quaking aspen (Populus tremuloides), somewhat after the man- 

 uer of the dolichopodid genera Medeterus or Netirigona. 



lOV. 



Tachydroinia bracliialis sp. nc 



Male Length 4 mm.-Black species covered with cinereous dust except sides 

 of thorax. Front and occiput cinereous dusted, lower occiput nearly devoid of 

 white hairs. Antenna yellow, the seta black. Proboscis reddish except the 

 extreme dark tip, palpi white, provided with a single black apical hair. Humeri 

 large concolorous with the remainder of the dorsum, scutellum with two erect 

 bristles, pleura shining black. Abdomen lightly cinereous dusted, the last seg- 



TEANS. AM. ENT. SOC, XXVIII. SEPTEMBER, 1902. 



