IGG NEW VOltK STATIC .MUSKUM 



The above description is copied from A'errall's paptM- in IMiil. 

 Trans. p.2l5, vol.KIS, only the nomenclature of the wing veins 

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

 fr(mi AVn-all, and illustrate details of the species L . p u s i 1 1 u s 

 Eaton, a small gnat found ;it Koyal Sound. Kerguelen Island. Xo 

 2S'orth American s|KH-ies. 



Genus 28. Chasmatonotus Loew 

 Berl. Ent. Zeit. p.51. ISGi 

 This genus is related to H y d r o b a e n u s 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-joiuted), 

 see i>1.31, iig.6. The dorsum of the thorax has a narrow fissure 

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

 (pl.ol, fig.lO) ; hence the name. The wings of our three American 

 species are black with white markings. 



KEY TO SPECIES OF CHASMATONOTUS 

 l))iaijillCS 



a Wing with two pi-oininent white spots (pi. 27, tisr.lC)) : the larger near 

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

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



1. b i m a c II 1 a t u s 

 (la Wing not marked in this way 



b 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 i>osterior margins of the segments 



whitish (Alaska) 2. uuivittatus 



hh Wing with a broad transverse band extending from the radius to the 

 posterior margin (New York) 3. u n i m a c u 1 a t u s 



1. Chasmatonotus bimaculatus Osten Sacken 



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

 1S7S Chasmatonotus O. S. Catal. Dipt. N. A. p.22 



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

 spots. Length about 1.5 mm. 



r>lack; 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, whicli is black. Knob of halteres greenish. 

 AVings 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, within the fork of the cubitus, 

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



