For extinct groups, see text Odonata is an order of predatory flying insects that includes the dragonflies and damselflies (as well as the Epiophlebia damsel-dragonflies).

[1] Johan Christian Fabricius coined the term Odonata in 1793 from the Ancient Greek ὀδών odṓn (Ionic form of ὀδούς odoús) "tooth".

[3] Odonata enthusiasts avoid ambiguity by using the term true dragonfly,[4] or simply anisopteran,[5] when they mean just the Anisoptera.

[6] The largest living odonate is the giant Central American helicopter damselfly Megaloprepus coerulatus (Zygoptera: Pseudostigmatidae) with a wing span of 191 mm (7.5 in).

The longest extant odonate is the Neotropical helicopter damselfly Mecistogaster linearis (Zygoptera: Pseudostigmatidae) with a body length of 135 mm (5.3 in).

Their mouthparts are modified, with the labium being adapted into a unique prehensile organ called a labial mask for grasping prey.

[18] The phylogenetic tree of the orders and suborders of odonates according to Bybee et al. 2021:[19] Zygoptera (damselflies) Anisozygoptera Anisoptera (dragonflies) In some treatments,[20] the Odonata are understood in an expanded sense, essentially synonymous with the superorder Odonatoptera, but not including the prehistoric Protodonata.

The systematics of the "Palaeoptera" are by no means resolved; what can be said however is that regardless of whether they are called "Odonatoidea" or "Odonatoptera", the Odonata and their extinct relatives do form a clade.

However, the combined suborder Epiprocta (in which Anisoptera is an infraorder) was proposed when it was thought that the "Anisozygoptera" was paraphyletic, composed of mostly extinct offshoots of dragonfly evolution.

The four living species placed in that group are (in this treatment) in the infraorder Epiophlebioptera, whereas the fossil taxa that were formerly there are now dispersed about the Odonatoptera (or Odonata sensu lato).

[22][23] World Odonata List considers Anisoptera as a suborder along with Zygoptera and Anisozygoptera as well-understood and widely preferred terms.

These include grasping cerci at the tip of the abdomen for holding the female, and a secondary set of copulatory organs located between the second and third abdominal segment in which the spermatozoa are stored after being produced by the primary genitals— whose external opening is known as the genital pore, on the ninth abdominal segment.

[29][30] Because the male copulatory organ has evolved independently from that in other insects, it has been suggested the stem-group dragonflies had external sperm transfer.

They then develop into instars with approximately 9–14 molts that are (in most species) voracious predators on other aquatic organisms, including small fishes.

The nymphs grow and molt, usually in dusk or dawn, into the flying teneral immature adults, whose color is not yet developed.

Because odonates are such an old order and have such a complete fossil record they are an ideal species to study insect evolution and adaptation.