50 A VE^'ATIONAL STUDY OF THE ZYGOPTERA 



6 (i). Secondary sectors few; a tendency to only one row of cells between Mia and 

 M2, if two rows, it is for a short distance only, M1+2 forking at less than one-half 

 the distance from the subnodus to the tip of the wing. Cih longer, ending at 

 one-half or more than one-half of the distance from the fork of Mi^2 to the tip 

 of the wing, at least in the fore wing. Cu> unbranched. One or two rows of cells 

 between Cua and the posterior wing margin. One row of cells between Ri and 

 Mi+2 before the fork of the latter 7 



7 (8). The nodus at one-fifth of the wing length. The hind wing, at least, tends to 

 have two rows of cells between Mta and i\l2 for a short distance. M4 has several 

 short sectors at its end ; there are two rows of cells posterior to Cu2. Mexico to 

 Colombia. (Fig. 49.) Pseudostigma Selys, i860 



8 (7). The nodus at one-fourth to one-fifth of the wing length. One row of cells 

 between Mia and M2. No sectors more than a few cells long, except between Mi 

 and M,a. M4 usually unbranched. One row of cells between Cu2 and the pos- 

 terior wing-margin. West Indies and Mexico to Ecuador. (Fig. 50). 



Mecistogaster Rambur, 1842 



Key to the Genera of the Subfamily Megapodagrioninae 



1 (2). Antenodals three to five, postnodals over fifty; venation very complex, many 

 supplementary' sectors from Mi to the posterior margin of the wing. About ten 

 cross-veins under the stigma. Quadrangle almost rectangular at both ends. 

 Wings not petioled to the level of the arculus. Panama to Costa Rica. (Fig. 5 1 .) 



Thaumatoneura McLachlan, 1897 



2 (i). Antenodals two to three, postnodals generally not over thirty; venation 

 simpler; supplementary sectors not usually present between Mi and Mu, and 

 Cui and Cu2. Cross-veins under stigma six or fewer. Quadrangle generally 

 acute diptally. Wings usually petioled beyond the level of the arculus 3 



3 (4). Rs arising one cell before the subnodus, M3 about one-half the distance be- 

 tween the arculus and the subnodus. Supplementary sectors Mia to Cu2. Wing 

 petioled to the level of one-third to one-half of the distance between the arculus 

 and MA. Formosa. (Fig, 52.) Rhipidolestes Ris, 1912 



4 (3) . Rs not arising before the subnodus. M3 arising nearer the subnodus than the 

 arculus ■ 5 



5 (30). Rs arising at or ven." near the subnodus, M3 at least one cell before the sub- 

 nodus " 



6 (7). Area posterior to Cu2 with four or five rows of cells. Wing petioled to or 

 beyond the level of the arculus. Supplementary sectors from Mia to Cui or Cu2. 

 Malaysia and Australia. (Fig. 53.) Podopteryx Selys, 1871 



7 (6). Area posterior to Cu-. with one or two, rareh' three rows of cells .8 



8 (19). Wing not petioled to the level of the arculus. it may be almost so in Tri- 

 neuragrion, a genus with a third antenodal 9 



9 (14). Short sectors present between Rsand M3 as well as some of the other longi- 

 tudinal veins - ^^ 



