Subfamily ArscHNINAE 
The Darners 
Very large and strong flying dragonflies, with nearly smooth bodies 
and rather brilliant coloration. The eyes meet broadly on the top of 
the semiglobular head, crowding between the visible part of vertex and 
occiput. The labium is cleft at the apex on the median line. The 
moderate stigma generally has a strong brace vein at its proximal end. 
The triangles are elongated in the axis of the wing and a trigonal 
planate springs from a prominence in the outer side of each. The fe- 
male has a well developed ovipositor. 
This family contains a large proportion of our biggest dragonflies. 
They dominate the upper air over pond and meadow. They venture far 
from water. They invade city streets and fly into open laboratory 
windows. 
These are the true ‘‘mosquito hawks’’; but their diet is by no means 
restricted to mosquitos. Midges and mayflies, and moths and crane- 
flies are eaten freely. When the evening swarms of mayflies rise by the 
waterside, these big darners may be seen coursing through the swarms, 
in and out again repeatedly, gathering a meal. At noon, when the 
midges are settled on the tree trunks by the water side, a big darner 
may often be seen searching a tree, his face a few inches from the bark 
as he slowly moves along it up and down on the leeward side, rustling 
his wings as if to flush the midges, and now and then seizing one of 
them. They all eat other smaller dragonflies. 
The nymphs of this group are smooth and slender of body with long 
thin legs. The labium is flat and lacks raptorial setae (except in Gyn- 
acantha); its median lobe is cleft at the front. The prothorax bears 
prominent tubercles at the sides. The abdomen is widened beyond the 
base. There is a considerable development of color pattern, suited to 
different types of environment. 
The nymphs are active climbers. They live amid green vegetation 
in still waters or in trash fallenin the edges of streams. They are pred- 
atory and cannibalistic, and often approach their prey by stealth. 
KEY TO THE GENERA 
Adults 
iechadial sector simple: 1.045.222. 6) 14 A PR SE ee 2. 
Radial sector bearing an apical fork (except in Oplonaeschna). .4. 
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