AMERICAN DIPTERA. 343 



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

 oval, only slightly longer than the second. Wings grayish hyaline, the costal 

 portion beyond the base of the subinarginal cell extending from the costa to the 

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

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

 thicker than the others. 3-4 mm. 



Behriug Island (Stejniger). 



Tachydroinia corticnlis 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 

 infuscated. 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 pleurae and scutellum with more cinereous dust, scutellum with two 

 erect widely separated bristles. Abdomen flattened, hypopygium large, shining 

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

 ing mainly 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. Cosfe and legs shining, piceous, front 

 ones lighter, the four anterior femora swollen, of nearly equal thickness, front 

 femora unarmed, ornate with two circular black spots on inner side below, one 

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

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

 front metatarsi also with minute setulae below; base of middle femora with a 

 rough pencil of black bristles fitting into the excised tip of the middle tibiae, 

 middle tibiae in length equalling their femora, provided with close minute setu- 

 lae on the under side; hind legs slender, their knees, middle part of tibiae 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 rajxix, running up and down the smooth trunks of 

 the quaking aspen iPopulus tremuloides), somewhat after the man 

 ner of the doliehopodid genera Medeterus or Neurigona. 



Taehydrouiia brachialis sp. nov. 

 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. Antennae 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, pleurae shining black. Abdomen lightly cinereous dusted, the last seg- 



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



