what are they ?
It is an insect belonging to the order Odonata, infraorder Anisoptera.
Introduction
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος "anisos", "unequal" and πτερόν "pteron", "wing", because the hindwing is broader than the forewing).
what are the life stages of a dragonfly Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges.
It is an insect belonging to the order Odonata, infraorder Anisoptera Most of a dragonfly's life is spent as a nymph. The larval stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. The adult dragonfly crawls out of its larval skin. A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera
Dragonfly Dragonfly Dragonfly
Introduction Life cycle Introduction
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος "anisos", "unequal" and πτερόν "pteron", "wing", because the hindwing is broader than the forewing).  Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος "anisos", "unequal" and πτερόν "pteron", "wing", because the hindwing is broader than the forewing). 
wiki:5424290
Dragonfly [SEP] Introduction
A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος "anisos", "unequal" and πτερόν "pteron", "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold the wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight.