Calvert : Odonata of the Neotropical Region. 155 



rilateral on the front wings with the anterior side less than half as long 

 as the posterior side, on the hind wings the anterior side more than 

 half, or half, as long as the posterior side. M 2 (= nodal sector of de 

 Selys) arising nearest the fifth postnodal on the front wings, the fifth 

 or fourth on the hind. Pterostigma and venation similar on front and 

 hind wings in both sexes. Abdominal appendages of the male similar 

 to those of Argia i. e. the superiors transversely, the inferiors verti- 

 cally, bifid. No ventral posterior spine on abdominal segment 8 of the 

 female. 



Type : Diargia bicellulata y sp. no v. 



This genus is closely related to Argia from which it differs in the 

 smaller number of biserial tibial hairs or spines (5-6 on outer side of 

 third tibia), the more proximal origin, as measured by number of 

 postnodals, of vein M„ and, in so far as the only known species is con- 

 cerned, by possessing but two antenodal ultraquadrilateral cells. From 

 Argiallagma Selys (cf. Calvert, Biol. Centr. -Amer. Neurop., p. 376) 

 it differs by the argiaform appendages of the male, the absence of a 

 vulvar spine in the female, and by the smaller number of antenodal 

 cells. 



Of the species of Argia known to me, Diargia most closely ap- 

 proaches Argia t/iisma, described as new in the present paper, page 

 141, under which heading will be found some details for comparison 

 with Diargia bicellulata. 



63. Diargia bicellulata, sp. nov. 



(Plate IV, figs. 67, 68, 68j; Plate VIII, fig. 141.) 

 r?. Black with the following parts pale yellow or blue : first anten- 

 nal joint anteriorly and all of the face and lips below the level of the 

 second joint of the antennae, a cuneiform postocular spot on each side 

 and a transverse occipital line connecting them, a narrow line bordering 

 the eyes posteriorly, front lobe 01 f he prothorax and the sides of the 

 other two lobes, an antehuL,eral stripe which at mid-height is one- 

 sixth as wide as the black mid-dorsal, a metepisternal stripe and a met- 

 epimeral stripe, neither of which is quite as wide as the black humeral 

 (mesepimeral) stripe, or as the black stripe present on the entire length 

 of the second lateral thoracic suture, an oval dorsal (blue) spot on 

 abdominal segment 2, a narrow transverse basal ring on 3-7 con- 

 fluent with a mid-dorsal line or narrow stripe on 3-5 or 6, reaching 

 the greater part of the length of each segment, sides inferiorly of 3-6 



