1882.] ^'Jl ■ [WilUston, 



Table of groups of genera. 



J. — Small cross-vein of the -wing distinctly before the middle of the 



discal cell, usually straight and rectangular. Hind femora usually 

 slender, not thickened ; the third longitudinal vein rarely much bent 

 into the first posterior vein, usually straight or very gently curved. 



1 — Antennae longer than the head I. 



2 — Antennie as long or shorter than the head. 



a — Marginal cell open, i. e., the second longitudinal vein terminates 

 in the border of the wing, 

 a — Face not tuberculate, nor distinctly cariuate ; not excavated be- 

 low the antennae in profile ; hyperstoma not produced. (Small, 



nearly bare species, with short oval abdomen) II. 



aa — Face tuberculate, or hyperstoma produced. 



*— Abdomen in outline, linear or oval, never narrowed toward 

 the base, or club-shaped. (Tegulse of usual size.) 

 f — -Body uniform metallic green, or metallic green and black ; 

 abdomen oval or elongate, never slender ; femora not thick- 

 ened, nor facial tubercle dissimilar in male and female . III. 

 If — Black with luteous, reddish or yellow, wlieu uuiformly 



black the hind femora thickened IV. 



tff — Black or greenish black, with yellow or yellowish stripes 

 or bands, or face more or less yellow. 

 g — Face black, abdomen slender, with yellow or greenish 



yellow interrupted cross-bands V. 



§§ — Face partly or wholly yellow, abdominal markings 

 yellow. 



-1-Dorsum of thorax with yellow lateral stripes VI. 



-- — Dorsum of thorax without yelloAV lateral stripes. VII. 

 -»* — Abdomen contracted toward the base," more or less club-shaped 



VIII. 



an — Marginal cell closed and petiolate IX. 



J J — The small cross- vein at or beyond the middle of the discal cell, 

 i. e., the discal section of the fourth longitudinal vein bej'oud the 

 small cross-vein, is but little longer or much shorter than the section 

 before it ; small cross-vein nearly always oblique, the posterior 

 femora frequently thickened. * 



a — Antennae with a distinctly dorsal bristle. 

 /3 — Third longitudinal vein bent deeply into the first posterior cell 



/' — Marginal cell closed and petiolate X. 



yy — Marginal cell open XI. 



l3fi — Third longitudinal vein gently curved. 

 d — Arista plumose. 



£ — Marginal cell closed IX. 



£=: — Marginal cell open XII. 



t'ifj — Arista bare or pubescent XIII. 



aa — Antennae with a subterminal bristle or terminal style XIV. 



J. —Small cross-vein before the middle of the discal cell. 

 1. Antennae longer than the head. 



A.— Scutellum flattened, with two obtuse points ; face evenly rounded, 

 pubescent, without tubercle ; eyes separated in both sexes, narrowly 

 in the male ; first posterior cell with a stump of a vein from the third 

 longitudinal ; dark or black species, unrelieved by light mark- 

 ings Microdon. 



