230 Journal New York Entomological Society, t^oi. xxi. 



rarely silvery-gray pruinose ; oral vibrissje often present ; frontal 

 suture usually arched, sometimes flattened 2. 



2. Costa broken twice, once beyond the humeral crossvein at which place there 



is usually a stronger costal bristle, and again just before the end of 

 the first vein ; hairs of oral margin borne wholly or largely on the 

 lower occiput which arches forward under the eye, the gense greatly 

 reduced, leaving the buccse more or less triangular, with the oral 

 vibrissa at its front angle ; face in profile concave, the vibrissal angle 

 often prominent and projecting as far as the level of the frontal 

 suture ; a double row of cruciate bristles present along the middle of 

 the front, borne sometimes on specialized stripes, the interfrontalia 

 often evident and formed from the enlarged ocellar triangle ; oral 

 margin often arched in front ; proboscis geniculate, and usually 

 lengthened, the labella rarely fleshy ; postverticals convergent, rarely 

 parallel or wanting, but never divergent ; anterior dorsocentrals, pro- 

 thoracic, and mesopleural bristles rarely present ; calypter small, rarely 

 densely ciliated ; anal vein entirely rudimentary or wanting. 



MiLICHIIX.E. 



Costa not, or but very rarely, broken at the humeral crossvein, and without 

 corresponding bristle ; bucca quadrangular or linear, or if triangular 

 usually broader behind, the occiput rarely reaching forward on the 

 cheeks, the hairs of the oral margin therefore together with the 

 vibrissa borne by the bucca ; face retracted or the vibrissal angle not 

 evident, produced only in some species of Rhicnoessa and Tethina ; 

 front usually devoid of cruciate bristles, though sometimes hairy ; 

 ocellar triangle usually reduced, insect often pollinose ; oral margin 

 not highly arched in front ; proboscis short, usually very short, labella 

 rarely chitinous ; prothoracic and mesopleural bristles usually pres- 

 ent ; calypter usually large and densely ciliate ; base of anal vein 

 usually evident 3- 



3. Postverticals divergent, rarely wanting; basal joint of arista minute, shorter 



than broad, the remainder of the arista closely short-pubescent ; aux- 

 iliary vein, though rudimentary, usually ending in the first vein instead 

 of in the costa (sometimes, e. g., Phytomyaa, Cryptochcetum, the 

 auxiliary vein parallels the first vein for its entire course) and rarely 

 {e. g., Agromyza spp.) it approaches the first for a short distance to 

 bend away at the tip ; the break of the costa at the end of the aux- 

 iliary vein, therefore, usually just in front of the termination of the 

 first vein; genae narrower than the buccse (except in Phytomyaa spp.) ; 

 upper occiput not deeply concave ; prothoracic bristle single. 



Agromyzin^. 

 Auxiliary vein more or less distinct from the first vein and ending separately 

 in the costa at a greater distance from the first vein than its separa- 

 tion from it along the middle of its course, rarely the end of the 

 auxiliary vein has completely vanished, in which case the fracture of 

 the costa some distance before the ending of the first vein indicates 



