166 NEW YORK STATE MUSEUM 



The above description is copied from Yerrall's paper in Phil, 

 Trans, p.245, vol.168, only the nomenclature of the wing veins 

 being changed. The flgiires 1 to 4 on plate 37 are also taken 

 from Yerrall, and illustrate details of the species L . p u s i 11 u s 

 Eaton, a small gnat found at Eoyal Sound, Kerguelen Island. No 

 North American species. 



Genus 28. Chasmatonotus Loew 

 Berl. Ent. Zeit. p.51. 1864 

 This genus is related to Hydrobaenus but differs from it 

 in that the palpi are longer, and the flagellum of the antenna 

 is composed of 5 joints in both sexes (i. e. antenna 7-jointed), 

 see pi. 31, fig.6. The dorsum of the thorax has a narrow fissure 

 which Widens posteriorly in a flat area in front of the scutellum 

 (pl.31, fig.lG) ; hence the name. The wings of our three x4.merican 

 species are black with white markings. 



KEY TO SPECIES OF CHASMATONOTUS 

 Imagines 

 a Wing \Yith two prominent white spots (pi. 27, fig.l6) ; the larger near 

 the base of the wing, the smaller subquadraugular, in the fork of the 

 c-ubitus, a little distad of the middle of the wing (New York, Illinois) 



1. bimaculatus 

 aa Wing not marked in this way 



6 Wing with a longitudinal vitta between the media and the cubitus; 

 thorax black with front corners, and hind end, and a part of the 

 pleura yellow ; abdomen with posterior margins of the segments 



whitish (Alaska) 2. univittatus 



bb Wing wath a broad transverse band extending from the radius to the 

 posterior margin (New York) 3. unimaculatus 



1. Chasmatonotus bimaculatus Osten Sacken 



1877 Chasmatonotus O. S. Bui. U. S. Geol. Surv. 3 : 191 



1878 Chasmatonotus O. S. Catal. Dipt. N. A. p.22 



Male. Black ; wings of the same color and with two large white 

 spots. Length about 1.5 mm. 



Black; thorax shining; base of the abdomen laterally pale 

 greenish yellow ; feet black ; front coxae and base of all the femora 

 yellowish; the first tarsal joints are of the same pale yellowish 

 color except the tip, which is black. Knob of halteres greenish. 

 Wings black ; the first white spot is in the shape of a cross band 

 between the second vein and the anal angle; second spot is square, 

 and situated on the hind margin, witliin the fork of the cubitus, 

 pl.27, fig.lG, pl.31, figs. G and 16, pl.32, fig.6. 



