508 



the tenth abdominal segment and setose on the ventral margin ; apical 

 margin of the tenth abdominal tergum cleft nearly to the base, the 

 margin thickly beset with short spines; gills (Fig. 58) uniform dark- 

 gray or nearly black, paler at the tip, long, broad, and bluntly pointed, 

 the margins parallel for a considerable distance. 



Measurements (young nymphs) 



Length 14 mm. 



Length of abdomen 9 mm. 



Length of gills 5-6 mm. 



Width of gills 3 mm. 



Length of metathoraeic wing-cases. . .4 mm. 



Length of median lobe 3.5 mm. 



Width of median lobe 1.5-3 mm. 



Described from a male specimen in the collection of the Illinois 

 State Laboratory of Natural History taken from the Kankakee River 

 six miles below Kankakee, June 1, 1901, and several specimens ob- 

 tained from Dr. E. M. Walker. 



Adult; Male. — Color, black and cinnamon-buff. 



Head: median lobe of the labium buff, subtriangular ; distal seg- 

 ment of the palpus dark at the tip; antennae black, first two segments 

 nearly equal, the first pale at the apex, the third segment longest ; clyp- 

 eus and labrum buff, the postclypeus with two indefinite black spots 

 near the f ronto-clypeal suture ; labrum with a mesal spot on the dorsal 

 margin ; front and genae buff, the pale color extending dorsad to the 

 ocelli, the black confined to an indefinite ring around the median ocellus 

 and wedge-shaped marks on the vertex ; occiput black ; the surface 

 of the head dorsad of the postclypeus and the occiput often becomes 

 pollinose and obscures the original coloration. 



Thorax : prothorax dark brown or black, more or less pollinose 

 with age ; caudal lobe of the pronotum black, median lobes each with 

 a large, pale, circular, median spot which often becomes pollinose be- 

 fore the rest of the notum ; proepimeron pale, the noto-epimeral suture 

 indistinct though marked by a black stripe ; dorsal carina black and 

 a black stripe on each side one-half the width of the mesepisterna : 

 mesopleural suture lined with black ; mesepimera with a broad sooty 

 line extending the entire length of the sclerite and more than half as 

 wide ; metapleural suture lined with black, the metepisterna and mete- 

 pimera and the postcoxal areas usually buff; legs rather short, striped, 

 the dorsum of all femora with a broad stripe including the cephalo- 

 ventral row r of setae ; tarsi and claws black ; wings clear, the stigma 



