M:\V VOKK SI-.\TI: .\ 



The above description is copied from Yen-all's paper in Phil. 

 Trans, p.245, vol.108, only the nomenclature of the wing veins 

 bring changed. The figures I to 4 on plate ::7 ;ire also t;ikeu 

 from Verrall, and illustrate details of the species L . p u s i 1 1 u s 

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

 North American species. 



Genus 28. Chasmatonotus Loew 



Berl. Ent. Zcit. p.51. ISOi 



This genus is related to Hydrobaenus but differs from it 

 in that the palpi are longer, and tin- llagellimi of the antenna 

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

 see pi. .'II. h'g.<i. The dorsiim of the thorax has a narrow lissure 

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

 i pl.::i . lig.Ki i : hence the name. The wings of our i hree American 

 species are black with white markings. 



KEY TO SPECIES OF CHASMATONOTUS 



I nnl'liii' * 



<i Win;: \\ith two ]ir<niiiiiei)t wliito spots i pl.'J". li^.li'.i; the larger near 

 the base of tin- win;:. Ilio smaller s>i]i<|iiailrangular, in the fork of the 

 ciiliitus. a little distad of the middle of the wini; (New York, Illinois) 



1. bimaculatus 

 an Win.L' not marUcd in this wa\ 



1) Winir \\-itli a longitudinal vitta bet wren Hie media and the cubitus ; 

 thorax black witli front corners, and bind end, and a part of the 

 pleura yellow; abdomen with posterior margins of the segments 

 whitish (Alaska) ............................. 2. univittatus 



bb AVin.L' with a broad transverse band, extending from the radius to the 

 posterior maririn (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.-' 



Male, lllaek ; 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, within the fork of the cubitus, 

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



