66 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



The known range of this species is from New Hampshire and Idaho 

 to New Jersey, Pennsylvania, Indiana, Colorado, and New Mexico. 

 In Massachusetts and Ohio it is known to occur in large n ambers 

 about gravel pits, railroad and highway cuts and fills which are 

 denuded or only scantily covered with vegetation, and strewn with 

 rocks and cobblestones. The adults may be seen in such places, 

 darting about just above the surface of the ground in characteristic 

 zigzag flight, and alighting from time to time on rocks or small stones. 

 Adults have not been taken on flowers. The host relationships of 

 this species are not knowm. 



SPHENOMETOPA NEBULOSA (Coquillett) 



Ar-aba nebulosa Coquillett, Canad. Ent., vol. 34, p. 200, 1902. 

 Sphenometo'pa nebulosa Townsend, Smithsonian Misc. Colls., vol. 51, 

 p. 64, 1908. 



Male with the front rather narrow, being 0.25, 0.27, 0.31, with an 

 average of 0.2S of head width; front much narrower at base of anten- 

 nae than at vertex; frontal rows not widely divergent below base of 

 antennae; parafrontals with row of one reclinate and two proclinate 

 orbital bristles back of which is a tuft of erect bristly hairs; arista 

 thickened on basal two-fifths, the penultimate joint distinctly shorter 

 than twice the width. Thorax gray pollinose, obscurely five vittate; 

 scutellum with three pairs of marginal bristles, of which the inter- 

 mediate pair is much the largest; abdomen flattened dorsoventrally, 

 truncate at apex, black overlaid with dense white pollen, with three 

 conspicuous black spots on dorsum of each one of the first three 

 segments sometimes coalescing apically; intermediate segments, and 

 usually the first v^dth a median marginal pair of bristles, fourth seg- 

 ment w^ith a marginal row. Wings hyaline with small but quite dis- 

 tinct smoky spots at the apex of second vein, the bend of the fourth, 

 the apex of the first, beyond the small cross vein and at the angle of 

 the fifth vein and the hind cross vein, a small niveous spot at extreme 

 tip of wing; apical cell narrowly open; last section of fourth vein 

 straight from bend to margin of wing; one small bristle at base of third 

 vein. Basitarsus of fore leg (pi. 3, fig. 18) conspicuously expanded 

 ventrally into a triangular segment having pale hairs on its ventral 

 margin. The female closely resembles the male, but its front is wider, 

 being 0.32 and 0.34 with an average of 0.33 of head width in two 

 specimens measured; the third antennal joint is slightly shorter, the 

 basitarsus of the fore leg is not modified, and the infuscated spots on 

 the wings arc less conspicuous. 



Length, 5.0 to 5.5 mm. 



Material examined: type, a male from Sierra Madra, Chihuahua, 

 Mexico, and another male from the same locality and apparently of 

 the type series (C. H. T. Townsend); one male and one female, 

 Florrisant, Colorado, labeled "on sand" (S. A. Rohwer); one male 



