arT. 21. DRAGONFLIES OF BURMA AND LOWER SIAM—LAIDLAW. 5 
Eyes usually in contact mid-dorsally for a long distance. Labium 
with median lobe slightly incised, or with a longitudinal depression. 
Female with complete ovipositor. 
Larva with elongated abdomen; mask flat, without setae (except 
in Gynacantha); lateral lobes narrow with apex of variable form; 
long movable hook. 
Gizzard with four radially symmetrical fields carrying a few large, 
specialized teeth. Respiration effected by rectal gills of the duplex 
form. (Tillyard). 
KEY TO THE ORIENTAL GENERA OF THE SUBFAMILY AESCHNINAE. 
1. Radial supplement straight, separated from radial sector or its lower branch by a 
single row (usually) of cells only. Median supplement similarly placed with 
regard to M,. (Larva with processus dorsalis usually pointed, not bifid at the 
APOK ee tetanes SOPs eee f eade we es biee “Re Ekh cece. 2 BRACHYTRON (group) 2 
Radial supplement curved concavely to radial sector, with three or more rows 
of cells between. Median supplement similiarly arranged with respect to M,. 
Radial sector unforked, or unsymmetrically forked. (Larvae with processus 
dorsalis bifid at apex) .. -.....-...-(AESCHNA group) 6 
2. Radial sector not forked, M, eek mlanked seventy ae just proximal 
to pterostigma. ewes appendage-strongly ‘Difid, be oe22/5h)- epee dF nohd< doped $3. 
Radial sector symmetrically forked; its branches ake a Oy 
(BRACHYTRON series) 4 
3. Venation open. Space between median supplement and M, with maximum 
breadth of two cells below the nodus for a length of two cells only... -.Jagoria. 
Venation dense. Space between median supplement and M, with two rows of 
cells, from before level of nodus to end of wing..................Linaeschna. 
4, Median space without cross nerves..............-.Austroaeschna-Planaeschna. 
Median space with cross nerves. g idea ae yee Fee Be 
5. Dentigerous plate of female CO or armed wih pe etiong Benes 
‘*Cephalaeschna”’ (Caliaeschna), 
Dentigerous plate of female armed with a pair of long decurved spines 
Periaeschna. 
6. Cells between Rs and Rspl arranged in very regular oblique rows. Anal angle 
of male hinder wing rounded, Rs unforked. M, with marked convexity for- 
ward under the pterostigma. Accessory longitudinal carinae on segments 3-8 
of abdomen. Dentigerous plate simple -............ (ANAX series) Anax, 
Cells between Rs and Rspl irregularly deririeede inal \anpile of male hinder 
wing pronounced. Rs forked usually distal to pterostigma. Dentigerous plate 
of female simple or armed with four or more spines. Diurnal forms. 
(AESCHNA series) 7 
Cells between Rs and Rspl irregularly arranged. Rs forked proximal to ptero- 
stigma. Anal angle of male pronounced. 
Crepuscular forms. Dentigerous plate or female armed with a pair of long 
decurved spines . ler .-.-------- (GYNACANTHA series) Gynacantha, 
7. M, with convexity Pema ploy: Gaetan Abdomen with traces of accessory 
lateral carinae on segments 4-7. ..-.....- .....-.. Anaciaeschna, 
M, without marked convexity forward. doen without subaasoy lateral 
Carinae nen . MSH. LL MW 8 Pf 
8. Dentigerone late n faulale, suapich jared only Sa eetally ee usually not 
regularly arranged |. aso o0.2).. 05. ee aR 
Dentigerous plate of female with fou or more windows spines, snes aeiédieon pair rie 
larger than the others. Wings rather sharply pointed .. ade tide +- 10 
