132 HELTCONID.E. 



disco-cellular nervure divides into two straight nervules at the point where it is joined by the 

 upper disco-cellular, which is directed almost perpendicularly downwards, instead of very 

 obliquely inwards, as it is in the males. Discoidal nervule appearing to be a fourth median 

 nervule. 

 Anterior Legs of the male very small ; the tibia and tarsus represented only by a small obovate 

 knob. Anterior Legs of the female with the femur and tibia nearly equal, the latter nearly 

 cylindric, slightly thickened at the apex. Tarsus about one half the length of the tibia. First 

 joint cylindric, longer than the rest combined, with a small spine on each side, a little before the 

 apex ; second and third joints thicker than the first ; the second scarcely one third, the third 

 scarcely one fourth its length, both armed at the apex with a stout spine on each side ; fourth 

 joint rather shorter than, and not so thick as, the third, furnished at the base with a tuft of stiff 

 hairs, covering the spine of the preceding joint ; fifth joint small, pointed, about as long as the 

 third. 

 Middle and Posterior Legs rather slender and elongate. Tibiae longer than the femora, slender, 

 spiny ; the spines not placed very closely, slender ; spurs distinct, but not remarkably so, from 

 the other spines. Tarsi not quite so long as the tibia?, spiny, the spines at the sides longest. 

 First joint cylindric, about one fifth longer than the rest combined ; second joint cylindric, less 

 than one third the length of the first ; third cylindric, about one fifth the length of the first, 

 equal to the fifth, which is broader, and elongate oval ; fourth joint short, broadest at the apex, 

 less than one sixth the length of the first. Claws rather small, much curved, grooved below. 

 Paronychia bilaciniate ; the outer lacinia linear, not so long as the claw ; the inner shorter, 

 broader towards the apex. 

 Abdomen elongate, slightly clavate, considerably longer than the inner margin of the posterior wings. 



Larva and Pupa unknown. 



In Sais, the variation from the normal structure of the posterior wings is more marked than in any previous genus, 

 for not only does the discoidal nervure in the males appear to be a fourth median nervule, but the second subcostal is 

 united to this in such a manner that it seems to be as much a fifth branch of the branch of the median nervule, as the 

 second of the subcostal. 



Other differences from the preceding genera will be found in the structure of the antenna;, the proportions of the 

 palpi, and in the legs. 



The anterior legs of the males have here sunk to their lowest point of developement. In Sais Rosalia they are only 

 one twenty-fifth part of an inch in length, or about one sixteenth of the length of the middle and posterior legs. It is 

 interesting to observe that this lowest degradation of structure in the anterior legs takes place in the same genus which 

 offers the greatest aberration from the normal structure of the posterior wings. The anterior legs of the female are 

 quite as much developed as in any of the preceding genera of this family ; when denuded of their scales, they appear 

 covered with delicate, satiny, closely oppressed hairs. 



In the small number of species belonging to this genus which I have seen, the wings are more or less transparent ; 

 the posterior pair in the males have the usual tuft of hair on the upper surface near the anterior margin. 



This genus seems to be nearly confined to the low wooded country drained by the Orinoco, the Amazons, and the 

 intermediate rivers. 



