AQUATIC INSECTS IN THE ADIRONDACKS 507 



db Triangle of the fore wing with its front and inner sides meeting by an angle 

 of about 90^; subtriaugle divided into three or more cells; bisector of the 

 anal loop sinuous 

 G Triangle of the fore wing not placed distinctly beyond the level of the 

 apex of the triangle in the hind wing; pterostigma with its ends parallel 

 or not distinctly divergent 

 d The sectors of the arculus (veins M1-3 and M4) in the fore wing more or 

 less completely fused for a short distance beyond the arculus ; the 

 triangle of the fore wing not greatly produced posteriorly, and 

 (except in Celithemis) normally containing but a single cross 

 vein, and followed by two or three rows of cells 

 e Vein Cui of the hind wing departing from the triangle at the hind angle 

 / Sectors of the arculus (veins M1-3 and M4) contiguous, but in- 

 completely fused for a distance beyond the arculus; wings 

 generally conspicuously spotted with yellow or reddish brown 



Celithemis p. 513 



ff Sectors of the arculus in the hind wing distinctly fused for a distance 



beyond the arculus 



g Stigma short and thick, about twice as long as wide ; anal loop 



with a big heel, there being generally four cells between the 



bisector and the heel point ; face pure white 



Leucorhinia p. 516 

 gg Stigma more than three times as long as wide ; anal loop generally 

 with but two cells between the bisector and the heel point' 



Sympetrum p. 519 

 ee Vein Cui of the hind wing migrated a little way up the outer side of 

 the triangle, separating itself at a distance from the hind angle 

 / With a single cross vein under the stigma, and a long vacant 



space before that cross vein Pachydiplax p. 526 



ff With two cross veins under the stigma and the adjacent spaces 

 more normal 

 g With a single row of cells between veins M2 and Rs 



Mesothemis p. 527 

 gg With two rows of cells for a distance between veins M2 and Rs 



Micrathyria p. 528 



dd Sectors of the arculus in the fore wing contiguous, but not completely 



fused beyond the point of their departure from the arculus ; radial 



sector distinctly undulate (except in Lad on a) ; triangle of the fore 



wing very much elongated posteriorly and narrow and generally 



traversed by two or more parallel cross veins, and followed by three 



to seven rows of cells 



e Vein Mia arising under the proximal fourth of the stigma; fore wings 



with the subtriaugle consisting of three cells, and the triangle 



followed by three rows of cells Ladoua p. 528 



ee Vein Mia arising under the middle of the stigma ; fore wings with the 

 subtriaugle consisting of four to 11 cells, and the triangle usually 

 followed by four to six rows of cells 



