154 Annals of the Carnegie Museum. 



Wings pale brownish-yellow, stigma surmounting more than one 

 cell (83.3 per cent, of both front and hind wings). 



Antenodal cells on the front wings 4 (83.3 per cent.) or 5 (16.7 

 per cent.), on the hind wings 4 (100 per cent.). Percentages based 

 on 3 ?. 



Dimensions. Abdomen 27-29; hind wing 23-24 mm. 



cT unknown. 



Habitat : — Paraguay, Sapucay, by W. T. Foster, November, 

 1899, three females, two of them numbered 16, the third 20 by the 

 collector (others numbered 16 are Argia fosteri). U. S. National 

 Museum. 



The specific name is in honor of Domingo Irala, founder of Asuncion. 



The mesostigmal lamina of this species is fairly large and strong, its 

 inner (mesial) end continued as a flattened ridge, which is directed 

 caudad, lies external to the fork of the lower (anterior) end of the mid- 

 dorsal thoracic carina, and gradually merges with the mesepisternal 

 surface anterior to the level of the forking of the mid-dorsal carina ; 

 the lamina itself is almost exactly transverse and its crest is largely 

 yellowish ; the continuation of the lamina as described above is paral- 

 leled in the female of A. tinctipennis ', q. v. 



A mesostigmal lamina very similar to that of iralai, except that it is 

 entirely black, is found in a female from Cachoeira, Brazil, by H. H. 

 Smith (no. 27), in the Carnegie Museum. This female, which may 

 be merely an older individual of iralai, has the black of the frons 

 reaching to the level of the antennae-bases, second antennal joint black 

 anteriorly, nasus obscure blackish, dorsal violet of abdominal segment 

 2 narrower, an inferior longitudinal brown or black line extending 

 forward from the blackish spot at the hind end of 3-7 almost to base, 

 dorsal black stripes on 9 confluent at anterior end of the segment. 



Abdomen 26, hind wing 21.5 mm. 



Diargia, gen. nov. 



Biserial hairs or spines of the basal halves of the second and third 

 tibiae twice as long as the intervals separating them, tarsal nails with 

 an inferior tooth. Vein A (= inferior sector of the triangle of de 

 Selys*) separating from the hind margin of the wing at least as far 

 proximad to the cubito-anal cross-vein (= postcostal cross-vein of de 

 Selys) as the latter is long. Arculus at the second antenodal. Quad- 



* Cf. Biol. Centr.-Amer. Neurop. p. 133, footnote |. 



