DIPLAX. 175 



3. D. costifera! 



Libellula costifera Uhler ! Mss. 



Yellowish ; thorax densely covered with long whitish hairs ; 

 second segment of the abdomen with a dorsal, triangular, fuscous 

 spot, the following segments having the lateral margin black ; the 

 vulvar lamina short, truncated, excavated, a little erected ; feet 

 yellow ; wings hyaline, the anterior margin and immediate base, 

 flavescent; pterostigma broadened, yellow; membranule white. 

 (Teneral female). Adult female : sides of the thorax whitish- 

 yellow, with a black vestige upon the posterior suture ; the abdo- 

 men is a little pruinose beneath, the eighth and ninth segments 

 have an ill-defined, longitudinal, black spot upon the middle ; the 

 femora have a black line exteriorly, and the tarsi are black. The 

 genital hamule of the male is bifid, the branches widely separated, 

 the posterior branch elongately-triangular, at tip a little decurved, 

 the anterior branch shorter, very slender, strongly recurved, acute 

 at the apex, the extreme point black ; genital lobe oblong, slightly 

 rounded at tip, hairy; denticles of the superior appendage sub- 

 equal ; inferior appendage but little shorter than the superiors, 

 triangular, rounded at the sides, ernarginate at tip, and with a 

 minute denticle each side ; t 8 antecubitals ; 5 6 postcubitals ; 

 three discoidal areolets. 



Length 35 39 millim. Alar expanse 58 60 millim. Ptero- 

 stigma 3 millim. 



Hob. Massachusetts (Scudder) ; New York (Edwards). 



4. D. vicina ! 



Diplax vicina Hagen I 



Yellowish-red ; front rufescent above, with a small, black band 

 before the eyes ; thorax and abdomen yellowish-red or altogether 

 yellowish (teneral); abdomen compressed at base, very much in- 

 flated beneath ; hamules longly bifid, the branches equal ; vulvar 

 lamina truncated, erect, excavated; feet yellowish-red; wings 

 hyaline, veins luteous, the extreme base flavescent ; pterostigma 

 oblong, luteous, broader in the middle; membranule whitish gray; 

 6 T antecubitals ; six postcubitals ; three discoidal areolets. 



Length 31 36 millim. Alar expanse 46 52 millim. Ptero- 

 stigma 2 J millim. 



Hob. Bergen Hill, New Jersey; Pennsylvania; Washington 

 (Osten Sacken). 



