Knab — On Some North American Species of Microdon. 139 



Microdon modestus, new species. 



Male. — Piceous black, without metallic luster. Frons broad, narrowing 

 slightly and regularly to posterior angles of eyes, where it is distinctly 

 more than one-third the width of the head ; transverse furrow arcuate, 

 indistinct, an elongate polished bare spot over insertion of antenna?; 

 vestiture of frons of black hairs with dirty yellowish ones intermixed, 

 particularly posteriorly and at the sides. Face clothed with black hairs, 

 some pale ones at lower margin. Antennae black; first joint long and 

 slender, about equalling longitudinal diameter of head ; second joint 

 slightly more than half as long as first, much enlarged distally ; third 

 joint hardly as long as first, much thickened on basal third and beyond 

 tapering to a sharp point ; arista a coarse piceous bristle, about equal in 

 length to third joint. Mesonotum piceous black, rather shining, clothed 

 with dull yellow hair, rather sparse on the disk and becoming dense to- 

 ward margins. Scutellum broadly rounded posteriorly, unarmed, con- 

 colorous with mesonotum and densely clothed with long dull yellow pile. 

 Abdomen elongate-ovate, flattened, much broader than the thorax, 

 broadest at third segment; color black, clothed dorsally with short but 

 rather dense black pile, the posterior margin of the second segment nar- 

 rowly yellow-haired and ending in patches of such hairs at posterior 

 angles; third segment with similar patches of yellow hair at posterior 

 angles ; fourth segment with a series of coarse pale setse at posterior mar- 

 gin. Genitalia piceous brown. Venter with scattered long pale hairs. 

 Legs black and clothed mostly with short black pile, the tarsi ventrally 

 with slightly paler hairs, on the hind legs their first two joints ventrally 

 \vi tli a dense cushion of dull ferruginous pile; pulvilli dull ferruginous, 

 claws black. Wings short, moderately broad, grayish hyaline, unspotted; 

 posterior angles of first posterior and discal cells roundedly produced, in 

 both with the vein-section closing the cell sinuate and bearing a very 

 short spur projecting inward. Halteres ferruginous yellow. Tegulae pale 

 yellowish. Length: Body about 13 mm., wing 10 mm. 



Female. — Frons similar to the male, still broader, the transverse furrow 

 obsolete; vestiture of frons and face almost wholly black. Mesonotum 

 clothed wholly with black hairs. Scutellum mostly black-haired, a few 

 whitish hairs intermixed. Abdomen wholly black -haired. Legs wholly 

 black, only the cushions of the tarsi indistinctly paler. Length: Body 

 about 11 mm., wing 8.5 mm. 



Elko, Nevada, 2 males, 1 female (no collector indicated). 



Type: Cat. no. 21,415, U. S. Nat. Mus. 



The type male has the hairs of the mesonotum and scutellum deep 

 brownish yellow, while in the paratype male this pubescence is a very 

 pale dirty yellow. 



Microdon senilis, new species. 



Female. — Black, without metallic luster. Frons at posterior angles of 

 eyes fully one-third the width of head, broadening gradually and evenly 

 to the face; transverse furrow obsolete, a narrow, smooth elevated stripe 



