SYNOPSIS OF NORffH AMERICAN SYRPHIU^. 153 



cross-vein, the distal part of the fourth vein, the posterior cross-vein, 

 and the veins at outer end of the second basal cell. 



A single specimen, Isthmus of Tehuantepec (National Museum, Pro- 

 fessor Riley's collection). This specimen, although I have but the one 

 for comparison, ofiers most excellent structural differences from G. 

 marginatum in the antennae, in the front being considerably narrower 

 above, and in the slender pilose stripe of the eyes. The pile on the eyes 

 of marginatum is black in the middle, but does not present the distinct 

 vittulate appearance; it is also throughout much longer in marginatum. 

 The broad, brown marking of the outer anterior i)art of the wings is 

 conspicuously different. The coloration of the body and legs is prob- 

 ably variable. On either side of the base of the antennae there is a 

 small, yellow spot, and the cheeks show an indication of a yellow stripe. 



SERICOMYIA.* 



Sericomya Meigen in Illiger's Magaz., ii, 274, 1803. 

 Large, robust, thinly pilose species, black, with yellow interrupted 

 fasciae on the abdomen. Head hemispherical, somewhat flattened. 

 Antennte short, third joint rounded or subquadrate, arista feathery 

 plumose. Face lightly excavated, or nearly straight below the antennae, 

 with a slight convexity near the middle, thence concave to the oral 

 border, descending moderately below the eyes, in profile obtuse. Eyes 

 bare, contiguous in the male. Abdomen elongate oval, broader than the 

 thorax, gently arched, nearly twice as long as the thorax. Legs strong, 

 hind femora sometimes somewhat thickened, hind tibiae somewhat bent, 

 at the tip sometimes with an angular protuberance. Marginal cell open, 

 third vein slightly, sometimes considerably, curved, anterior cross-vein 

 a little before or near the middle of the discal cell, a little oblique. 

 Type of genus, S. borealis Fallen, Europe. 



TABLE OF SPECIES. 



1.— Black facial stripe very broad ; bauds of abdoineu yellowish white (?) . lappona 



Facial stripe moderately broad; bands of abdomen more yellow 2 



2. —Second abdominal segment with two yellow dots, or wholly black ; hind femora of 

 male considerably thickened militaris 



Second abdominal segment with a median, interrupted fascia 3 



3. — Yellow abdominal bauds broadly interrupted, the si>ots more or less elougate 

 hour-glass shaped sexfasciata 



The yellow bands narrowly interrupted, the spots not constricted .... 4 

 4. — Fourth segment (in the male at least) without yellow cross-band . . bifasciata 



Fourth segment with cross-band like those of preceding segments .... 5 

 5. — Abdominal spots distinctly o1)lique chrysotoxoides 



Abdominal spots transverse chalcopyga 



* ^7)piKoc, silken, and fivia, a fly. 



