SYNOPSIS OF NORTH AMERICAN SYRPHID^. 207 



TABLE OF SPECIES. 



a.— Femora black, at the tip testaceous; the hind femora below, uear the base, with a 

 strong mammiform process ( <? ) mamillata 



b.— Front and middle femora yellow on distal end ; hind femora without such process 

 near the base quadrata 



c— Antenna} large, reaching nearly to the oral margin; hind cox* of male with a 

 large obtuse spur calcarata 



Tropidia quadrata. (Plate IX, tigs. 2a, 2b.) 



Xi/lota quadrata Say, Amer. Ent,, i ; tab. viii ; Compl. Wr., i, 14 ; Wiedemann, 



Auss. Z,w. Ins., ii, 101, t> (translation from Say). 

 Tropidia quadrata Macquart, Dipt. Exot., ii, 2, 72. 

 ? Tropidia albistylum Macquart, Dipt. Exot. 2e Suppl., 60, 1 ; tab. 2, fig. 10. 



Sahitat.—l^ew England, Canada, Washington Territory ! 



5,9. Length, 9 to 12™°^. Front in female narrow above, black, shining 

 below and at the vertex, on the sides thickly yellowish gray-dnsted; pile 

 very short and sparse, yellowish. Vertical triangle small, black, with 

 black pile: frontal triangle small, colored like the face. Face gently con- 

 vex in profile in the male, a little concave near the middle in the female ; 

 in color reddish or brownish yellow, densely covered with yellowish 

 gray pollen, leaving a slender median stripe shining black, a stripe 

 or spot on the cheeks also black. Antennae reddish yellow, the third 

 joint nearly sqnare. Dorsum of thorax shining, greenish black, with 

 two rather distinct median poUinose stripes, narrowly separated, be- 

 coming obsolete near the middle ; two spots of the same colored pollen 

 in front of the scutellum, another in front of each post-alar callus, on the 

 humeri, and a spot along the dorso-pleural suture immediately behind 

 the humeri. Pleurae wholly thickly whitish pollinose. Scutellum yel- 

 low along the border. Abdomen reddish-yellow ; in the male the first 

 segment black, whitish pollinose, yellow on the sides ; second segment 

 in front (but not reaching the sides) and a narrow median stripe black, 

 behind extending narrowly to the sides, more brownish, or only 

 slightly brownish, except at the outer ends, forming an inverted T, 

 posterior margin of the segment yellow ; third segment with a median 

 narrower black or brown stripe, not reaching the front, and on the 

 hind part more or less indistinctly brownish like the preceding ; fourth 

 segment on the disk mostly brownish-black with yellowish pollen. In 

 the female the black on the second segment is broader; the third seg- 

 ment black, except a quadrangular spot in front on each side, and the 

 hind margin, yellow. Front and middle legs, on the basal half or more of 

 the femora, black, reddish yellow elsewhere, except that the tibii^e may 

 be somewhat brownish before the tip. Hind legs black, the knees only 

 yellow. Wings hyaline, third longitudinal vein moderately bent into 

 the first posterior cell. 



Twenty-nine specimens, Canada (Brodie), Washington Territory (Mor- 

 rison), Connecticut. 



The synonymy of T. albistylum seems probable ; the only difference 



