136 
Psyche 
[June-Sept. 
A NEW GENUS OF PERLIDAE 
By Nathan Banks 
Museum of Comparative Zoology, Cambridge, Mass. 
The sternal structures of Perlidse have not been investi- 
gated as fully as some other parts of their structure. In 
examining Acroneuria for some structure to distinguish the 
females from other Perlidse, I noticed that in two of our 
species the grooves on the meso- and metasterna were dif- 
ferent from other species of Acroneuria. In the figures I 
have shown the differences. In the typical Acroneuria the 
anterior grooves are widely devergent, in A. pacifica they 
are short and nearly parallel. This sternal difference is 
correlated with the broader ocellar triangle, and the position 
of the lateral bosses, as well as in the last segment of the 
male. I shall, therefore, make A. pacifica the type of a new 
genus. 
Hesperoperla gen. nov. 
Anterior meso- and metasternal grooves short and nearly 
parallel ; the ocellar triangle plainly broader than long ; the 
lateral bosses on a level with the anterior ocellus; in the 
male the last ventral segment has a nearly quadrangular 
boss instead of the usual elliptic or rounded one ; in the fore 
wing the second anal vein is frequently forked (rarely in 
Acroneuria). In Acroneuria the ocellar triangle is as long 
as broad, and the lateral bosses are higher. In Beloneuria 
the anterior sternal grooves are somewhat as in Hespero- 
perla, but curve outward more, but not nearly as much as 
in Acroneuria; the lateral bosses are higher, although the 
ocellar triangle is broader than long ; the peculiar structure 
of the last ventral segment of the male in Beloneuria, some- 
what like that of some Pteronarcys, will readily distinguish 
this genus, as well as the irregular apical venation. 
Genotype : Acroneuria pacifica Bks. 
