1947] 
Banks — Characters in the Perlidce 
277 
and the forks slope behind the sector, so sector 
fairly parallel to radius ; usually some cross-veins 
beyond the cord; last joint of maxillary palpi 
usually one-half of fourth joint. In male no proc- 
ess or extension of fifth dorsal segment, but on 
ninth ventral segment is a raised median disc; 
subcosta often ends beyond cord Acroneurinae 
Radial sector usually with but two forks and the first 
parts into an anterior as well as posterior branch ; 
no series of cross-veins beyond cord, subcosta often 
ends before or at cord ; last joint of maxillary palpi 
usually not one-lialf of fourth joint. In male the 
fifth segment is usually extended, and the genital 
prongs wholly visible from above, no median disc 
on the ninth ventral segment Perlinae 
9. Both wings with cross-veins beyond the cord forming 
several irregular cells; the portion of fore wing 
beyond cord rarely a third of wing-length; the 
cubito-anal cross-vein is well beyond the end of 
anal cell ; ocellar triangle usually as long as broad ; 
anal lobe distinct and quite long Perlodinae 
Wings rarely with cross-veins beyond the cord, and 
not forming several cells ; portion of fore wing 
beyond cord usually fully one-third of wing- 
length ' 10 
10. In the forking of the cubitus in the fore wing the 
upper branch bends a little upward at the forking, 
while the lower branch also bends down a little, 
rarely in a curve or else does not bend at all. 
Radial sector often forks two or more times. 
Often with more than one cubital cross-vein in hind 
wings ; cubito-anal vein sometimes broken 11 
In the forking of the cubitus, it is the upper branch 
which continues the straight course, and the lower 
one diverges usually in a curve. Radial sector 
rarely forks more than once, and usually but one 
cubital cross-vein in the hind wings. The fourth 
joint of antennae is usually as long as broad, and 
the sense-hairs distinct ; median groove rarely 
present ; cubito-anal vein normally not broken. 
Isoperlinae 
