The family Aeshnidae consists of Darners (in the Americas) or Hawkers (in most of the rest of the world). They are large dragonflies with large eyes and long abdomens that fly continuously or hover intermittently, then hang vertically when they perch. Some individuals may land horizontally on logs, rocks, or the ground to warm themselves in the sun at lower temperatures. The abdomen, especially of the male, is swollen at the base and often constricted at S3. Male cerci in most are long and fairly simple and make the abdomen seem longer. Female cerci also typically are long and often distinctive, but in many species are broken off during oviposition, so the female abdomen looks thicker and shorter than that of the male. Females have well-developed ovipositors, unlike most dragonflies. The thorax in most shows two side stripes, and the abdomen usually has a complex pattern of pale spots. They are the only fliers that have blue coloration on their bodies. Other flier dragonflies are spiketails, river cruisers, and emeralds. Spiketails have much smaller eyes, not quite or barely touching in middle, and black or dark brown bodies with two yellow stripes on either side of thorax (many darners share this, but their base color is brown rather than black). River cruisers have large eyes but only a single stripe on each side of the thorax and large central spots or rings on the abdomen, darners paired spots (some are ringed). Most emeralds have brilliant green eyes and brown or metallic black and green bodies, sometimes with green highlights. Female darners have well-developed ovipositors, whereas spiketails have a pointed, projecting subgenital plate, and river cruisers and emeralds lack any special modifications for egg laying. Wing venation also distinguishes families. Wings tend to become suffused with yellowish to brown in older darners.
Paulson, Dennis. Dragonflies and Damselflies of the East (Princeton Field Guides Book 80) (p. 167).
