TO DIPTERA OF NORTH AMERICA. [PART IV. 



D. C. ; New York, etc. Wisconsin (Kennicott). The infuscated 

 marginal cross-vein is a very good distinctive character of this 

 species. 



This species is apparently identical with a European one, a 

 specimen of which is in my possession. I cannot determine the 

 latter with any degree of certainty, but the description of D. tristis 

 Schum. agrees tolerably well with it. 



12. D. tiaeretica, n. sp. % and £ • — Cervina, thorace vitta fusca ; 

 antennae nigrse ; rostrum ochraceum ; palpi fusci ; alae cinerascentes, 

 immaculatse ; praefurcae initium apici venae auxiliaris plus minusve 

 oppositum. 



Drab colored, thorax with a brown stripe ; antennae blackish, rostrum 

 yellow, with brown palpi ; wings with a grayish tinge, immaculate ; the 

 origin of the praefurca is nearly opposite the tip of the auxiliary vein. 

 Long. corp. 0.3—0.35. 



Head brownish, finely sericeous with yellowish ; rostrum yellow, 

 palpi brown ; antennae brownish-black. Thorax brownish, finely 

 sericeous with brownish-yellow; this sericeous dust being the 

 thickest on the sides, leaves a brown stripe in the middle ; pleurae 

 brownish, or, in some specimens, pale ; sericeous with yellowish ; 

 scutellum and metathorax brownish, likewise dusted with whitish- 

 yellow. Stem of halteres pale towards the basis, knob brown ; 

 abdomen brown above, venter paler. The forceps of * the male 

 is rather large and conspicuous even in dry specimens ; in fresh 

 specimens the reniform lobes appear somewhat club-shaped at 

 one end, that is, broader at the tip than in the middle ; the upper 

 valves of the ovipositor are remarkable for their extreme small- 

 ness. Coxae and basis of the femora yellowish ; feet tawny, tip 

 of the tibiae slightly infuscated ; tarsi brown towards the tip. 

 Wings (Tab. I, fig. 3) with a slight brownish-gray tinge, veins 

 brown ; stigma pale (slightly infuscated along the cross-vein in 

 one of the specimens from Fort Resolution). Tip of the auxiliary 

 vein nearly opposite the origin of the second vein ; subcostal 

 cross-vein removed from this tip at a distance a little less than 

 the length of the great cross-vein ; the marginal cross-vein is near 

 the tip of the first longitudinal vein, and is placed in such a man- 

 ner that it looks as if the first longitudinal vein was incurved 

 towards the- second and connected with the costa by the cross- 



