Knob — On Some North American Species of Microdon. 143 



longitudinal diameter of head ; third joint over one-and-a-half times the 

 length of the first, nearly parallel-sided, slightly compressed, the end 

 bluntly rounded off, the surface clothed with very fine and dense pubes- 

 cence ; arista consisting of a ferruginous yellow thickened portion which 

 is stoutest at its middle and about half the length of the third joint, and 

 a fine white bristle about two-thirds the length of proximal portion. 

 Mesonotum piceous, shading to dark reddish brown at the sides; vestiture 

 rather long, moderately dense, of pale yellow hairs. Scutellum con- 

 colorous with mesonotum, rather prominent, depressed distally, at tip 

 truncate and with thickened margin, unarmed ; vestiture of rather dense 

 and long yellow-brown hairs. Postnotum black, shining. Pleurae piceous, 

 shining, brownish yellow at the sutures, with a few patches of yellow 

 hair. Abdomen elongate-ovate, broadest at apex of second segment, 

 then tapering gently to the broadly rounded tip; integument dull brownish 

 black stained with brown, an ill-defined median stripe visible on third 

 and fourth segments; vestiture of rather dense, long fine hairs with pale 

 yellow silky luster, nearly evenly distributed but visible only in some 

 lights and therefore giving the appearance of large bare areas. Legs 

 rather stout, the coxse and femora yellowish brown, the latter broadly 

 yellow at the apices ; tibiae deep ocher-yellow, with a narrow brown ring 

 at middle ; tarsi ferruginous yellow ; vestiture of rather dense yellow 

 shining hairs, the tarsi ventrally with cushions of golden pile. Pulvilli 

 ocher-yellow. Claws black on distal half. Wings broad, the integument 

 smoky and distinctly hairy, extreme base brown, some brown cloudings 

 in the costal region and on the cross-veins ; first posterior and discal cells 

 with the posterior angles blunt and somewhat produced, each with a dis- 

 tinct spur, the usual spur projecting from third vein into middle of first 

 posterior cell. Tegulse and halteres ocher-yellow. Length: Body about 

 8 mm., wing 6 mm. 



Baracoa, Cuba, September, 1901, one male (A. Busck). 



Type: Cat. no. 21,418, U. S. Nat. Mus. 



The specimen just described appears to enter very well into the genus 

 Ceratophya as originally defined by Wiedemann, in the light of our 

 present knowledge the genus seems hardly tenable; it connects with 

 typical Microdon through species having the different characters variously 

 developed and modified, so that no line can be drawn between them. 



