SYNOPSIS OF NORTH AMERICAN SYRPHIDiE. 



289 



/Ve^—Coraposed of the five joints of the tarsi, the basal one of which is called the 

 metatarsus, the distal one terminating in two clatvs or ungues, on the under side of each 

 of which is a small membranous ai)pendage, the pulvillus. 



WINGS. 



Horders or margins, anterior, exterior, and posterior of the wing, directed transversely. 



Aliilet.— The lobe or flap of the wing, without veins, on the basal posterior part. 



Venation.— Costal vein, the one bordering the anterior margin of the wing ; auxiliary, 

 nearly parallel with the eosta from the base, and terminating in that vein near its 

 middle; connected towards its base with the costa by a transverse cross vein, the 

 humeral cross-vein ; the first longitudinal vein arises from the auxiliary-vein in the 

 vicinity of the humeral cross-vein, follows the auxiliary subparallel, and is inserted 

 in the costa; the second longitudinal vein arises from the first longitudinal a little 

 beyond the humeral cross- vein, follows the former, and is inserted in the costa, or some- 

 times in the first vein before its tip ; the third longitudinal arises by a fork from the 

 second longitudinal, a little distance before the termination of the auxiliary, and is 

 inserted in the costa at its tip ; in its course it gives off a short branch, the anterior 

 or small cross-vein, to connect with the fourth longitudinal vein ; fourth longitudinal 

 vein arises from the second main vein-stem opposite the humeral cross-vein and 

 terminates in the third longitudinal a short distance before its tip; it gives off, first 

 the anterior basal cross-vein behind, opposite the origin of the third vein, second the 

 anterior cross-vein to connect with the third longitudinal, and, just before it bends 

 forward to connect with the third vein, it receives the posterior cross-vein; ihe fifth 

 longitudinal vein arises near the origin of the fourth and terminates a little before the 

 posterior border of the wing ; opposite the anterior basal cross- vein it gives off the 

 posterior basal cross-vein, is then directed angularly forwards to join the anterior basal 

 cross- vein, then follows parallel to its first section to connect with the posterior cross- 

 vein where it terminates, or is sometimes extended a short distance as a stump ; the 

 nixth longitudinal rein arises near the origin of the tiitb aud terminates in or near the 

 posterior border of the wing, a little before the iiiiddle : just before its end it receives 

 the posterior basal cross-vein. 



Antcrc-is-\i 6.t.v. 'i.lcnvy. 

 Pdit.baSttTci'osi-v. 



"Wins (if Eriafalh. 



The costal cell is included between the auxiliary vein aud the costa. The subcostal 

 cell is bounded in front by the auxiliary vein and the costa, behind by the first longi- 

 tudinal. The marginal cell is inclosed by the first and second longitudinal veins, 

 wholly when the cell is closed, in part in front by the costa when the cell is open. 

 The submarginal cell lies between the second and third veins, touching the costa 

 exteriorly for a short distance, and the tip of the first longitudinal vein when the 

 inarginal cell is closed. The first basal cell is bounded in front by the basal sections 

 of the first, second, and third longitudinal veins, exteriorly by the anterior cross-vein, 

 posteriorly by the fourth longitudinal vein. The second basal cell is bounded in front 

 by the fourth longitudinal vein, exteriorly by the anterior basal cross-vein and the 

 second section of the fifth longitudinal vein, posteriorly by the fifth longitudinal. 

 The third basal, or anal, cell is bounded in front by the fifth longitudinal vein, ex- 



