228 DIPTERA OF NORTH AMERICA. [PART IV. 



cils short, bristle-like. Thorax yellowish-gray above, with four 

 brown stripes, the intermediate ones approximated ; the lateral 

 ones extend over the suture behind ; pleurae, scutellum, and meta- 

 thorax grayish ; halteres pale ; feet very long and slender, dark 

 tawny, tips of the femora and of the tibise darker ; tarsi brown. 

 Abdomen brownish-gray ; forceps likewise ; ovipositor ferru- 

 ginous. Wings (Tab. II, fig. iy with four or five brown spots 

 along the anterior margin ; the third one is usually prolonged in 

 the shape of a band, over the central cross-veins as far as the fifth 

 longitudinal vein ; the fifth spot, at the tip of the anterior branch 

 Oi^ the second vein, is often wanting f the posterior end of the 

 discal cell, and the inner end of the second posterior cell are 

 likewise spotted with brown. Marginal cross-vein at the tip of 

 the first longitudinal vein ; anterior branch of the second vein 

 arcuated, almost angular, near the basis ; petiole of the first sub- 

 marginal cell about the length of the great cross-vein ; second 

 submarginal cell only a trifle longer than the first posterior ; 

 discal cell elongated. 



Hab. United States. It is a common species, and occurs 

 in abundance especially in rocky localities, alighting upon the 

 stone ; I found it in this situation along the Hudson River Rail- 

 road, near New York, in abundance. 



The spots vary in intensity as well as in size ; those at the tip 

 of the second vein and at the inner end of the second posterior 

 cell are among the first to disappear; the other brown marks are 

 apt to become very pale, almost obsolete. I possess a couple of 

 specimens with an adventitious cross-vein in the first submarginal 

 cell, opposite the marginal cross-vein. Another specimen has an 

 adventitious cross-vein in the marginal cell, near the inner end 

 of the first submarginal cell. 



The forceps of the male of this species is very peculiar ; 

 instead of the usual horny appendages, it has a pair of elongated, 

 digitiform, soft appendages, which do not overlap each other in 

 repose (Tab. II, fig. 26 and 26 o). The ovipositor has short, 

 rather broad upper valves, abruptly tapering towards the tip. 

 The structure of the forceps and of the antennse, and the peculiar 

 venation, have induced me to propose for this species the sub- 

 generic name of DactyloJabis (compare above, p. 198). 



' The figure shows ovily the veins aud not the spots. 



