Aeshnidae

The Aeshnidae is a cosmopolitan family with moderate species richness. Aeshnids are strong flyers and active hunters; they fly nearly continuously and hover intermittently. Nymphs of 12 of the 13 genera of Aeshnidae that occur in Thailand are keyed and diagnosed. High-quality photographs of the dorsal and ventral habitus, as well as details of the morphology, are provided. The nymph of Oligoaeschna is still unknown. Aeshnid nymphs have relatively short, usually 7-segmented antennae, a flat prementum, 3-segmented tarsi, and a fusiform abdomen. The genera are distinguished by palpal shape, presence/absence of long palpal setae, posterolateral and dorsal spines on the abdomen, epiproct shape, and relative lengths of the caudal appendages. Most of the species inhabit lentic environments, including phytotelmata, although Tetracanthagyna is a notable stream-dwelling genus. Aeshnid nymphs are active climbers and can be found among submerged roots, aquatic plants, and dead stems that have fallen into the water; they are fierce predators, attacking even tadpoles and small fish.