* SYNOPSIS OP NOETH AMERICAN SYRPHID^. XV 



a limited classification may happily admit of a far wider application. In 

 such a family as the Syrphidai many disturbing elements must naturally 

 intrude themselves with the ingress of new forms; but the knowledge 

 of the world's fauna can only be obtained from the assimilation of more 

 or less heterogeneous parts into one homogeneous whole. My autoptic 

 knowledge of genera is almost exclusively confined to the European and 

 North American forms, types of nearly all of which 1 have examined. 



SYNOPTIC TABLE OF TRIBES. 



a. Anterior cross- vein of the wiugs distinctly before the middle of the discal cell, 



usually nearly rectangular ; third longitudinal vein rarely with a 

 distinct curvature into the first posterior cell ; hind femora rarely 

 thickened. Usually smaller, more delicate species, generally thinly 

 pilose ; SYRPHIN^. 



b. Third joint of the antennae with a thickened styliform arista or style. 



Pelecocerini. 

 bh. Antennae with a dorsal bristle. 



0. Third joint of the antennae not both elongate and with a strongly plumose 



arista ; marginal cell open. 



d. AntennjB longer than the head, rather large species Microdonini. 



dd. Antenuae not longer than the head. 



e. Front long, much narrowed above in the female, cheeks narrow, face considera- 



bly narrowed below, abdomen frequently contracted beyond the 



base, more or less slender Bacchini. 



ee. Face not remarkably narrowed below. 



/. Epistoma projecting, face without tubercle; abdomen contracted toward the 

 base, in outline more or less club-shaped ; small species. 



Spheginini. 

 ff. Not such species. 



g. Color chiefly reddish or lutescent Brachyopini. 



gg. Color not chiefly reddish or lutescent. 



h. Metallic green, metallic green and black, or black species, rarely with luteous 

 markings at base of abdomen, and on the humeri and face ; abdo- 

 men never with entire shining cross-bands Chilosini. 



hh. Black or greenish black species with yellow or yellowish stripes and bands, or at 

 least with entire shining cross-bands on abdomen. 



«. Face black Melanostomini. 



ii. Face partly or wholly yellow Syrphtni. 



cc. Third joint of antennae elongate, with a strongly plumose arista ; marginal cell 



usually closed ; thick-set species Volucellini. 



aa. Anterior cross- vein near or beyond the middle of the discal cell, usually oblique; 

 hind femora frequently thickened. Usually larger, robust, pilose 

 species. 



;'. Antenuae with a dorsal bristle ERISTALIN^. 



k. Third longitudinal vein bent deeply into the first posterior cell Eristaxini. 



kk. Third longitudinal vein only gently curved or straight. 



1. Arista plumose. 



m. Third joint of antennae elongated Volucellini. 



mm. Third joint of auteniue subquadrate; marginal cell open Sericomyini. 



II. Arista bare or pubescent. 



«. Thorax with distinct yellow markings Milesini. 



nn. Thorax without yellow markings Xylotini. 



jj. Antennae with a terminal style CER1N.31.' 



