588 GEOLOGICAL SURVEY OF THE TERRITORIES. 



in Illinois by Mr. Walsh. There are a few teneral specimens from the 

 foot-hills of Colorado, June 25 to July 6. 



If. longipennis, Hagen, Hayden's Eeport, 1872, 728. 

 Eahitat. — Yellowstone (C. Thomas). A species common everywhere. 



DIPLAX. 

 D. atripes, sp. nov. 



Male. — Eeddish-brown, snbvillous; labium, labrum, and head reddish ; 

 frontabove near the eyes with a large, blackish, transverse band ; vertex 

 reddish, large, inflated, smaller at the tip, with the angles not well 

 marked ; occiput reddish-brown, villous ; eyes behind reddish-brown, 

 with transverse blackish spots. Prothorax reddish, black beneath, the 

 posterior lobe with very long hairs ', thorax clothed with brownish hairs, 

 reddish-brown, the mesothoracic crest and the sutures on both sides 

 blackish. Abdomen reddish ; ventral margin of segments 7 to 9, with a 

 large black band ; appendages reddish, villous, the superiors cylindrical, 

 straight, somewhat thicker for the tip, with about five small teeth ; tip 

 shortly-i)ointed ; the inferior a little shorter, triangular, somewhat 

 smaller toward the apex ; the tip bent upward, with two small teeth ; 

 genital parts of the second segment with the hamule black, bifid, the 

 branches not very widely separated, the external stouter, elongately 

 triangular, a little decurved at the tip ; the internal shorter, slender, 

 strongly recurved, acute at the apex; genital lobe oblong, rounded at 

 the tip, interiorly inflated; anterior lamina with a small tooth in the 

 middle of the margin ; feet black ; the anterior femora pale-brown 

 beneath ; wings hyaline, with a faintly smoky tinge ; the -extreme base 

 flavescent ; membranula white ; veins reddish-yellow ; pterostigma 

 oblong, reddish ; 7-8 antecubitals ; 7 postcubitals. 



Female. — Similar to the male, jialer ; head yellow ; dorsum of the 

 thorax pale-brown, sides yellowish, with three wavy, blackish lines on the 

 sutures ; abdomen luteous ; a large black band on the ventral margin, 

 and another above it not reaching the apex ; segments 7-9, with a 

 black dorsal band in the middle; appendages yellowish, cylindrical; 

 vulvar lamina short, truncated; feet as in ^ ; trochanters yellowish ; 

 in teneral females all femora above in part yellowish; wings as in <?, 

 the base larger, flavescent ; sometimes also the costal border to the 

 pterostigma. 



Length of the body, 5, 30-38 millimeters; 9, 31-35 millimeters; 

 alar expansion, $, 43-60 millimeters; $,52-58 millimeters; pteros- 

 tigma 1^-2^ millimeters. 



iTa&iiftt— Yellowstone ; some pairs in copula (Mr. Garpenter). This 

 species is nearly related to D. costifera, but different by thjd black color 

 of the feet. 



D. decisa, sp. nov. 



Similar in shape and colors to D. vicina ; labium luteous ; labrum and 

 head in front yellow ; front above deeply canaliculated, discolored ; a 

 large black band before the eyes ; anteunse black ; vertex nearly 

 globular, the anterior angles obtuse, luteous, black around the ocelli ; 

 occiput luteous ; eyes behind luteous, with two transversal brownish 

 bands ; thorax reddish-brown ; on the dorsum a brownish tinge, dilated 

 triangularly to the prothorax ; abdomen reddish-brown ; sutures yellow- 

 ish, a black, lateral band dilated behind on the ventral margin of seg- 

 ments 3 to 9 and two yellow dorsal spots, nearer to the base ; abdomen 

 beneath pale-brown; margin of segments 4 to 7 black; venter black; 



