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Suborder Anisoptera - Dragonflies

Ocellated Darner - Boyeria grafiana - male Female White-faced Meadowhawk? - Sympetrum Bue-eyed darner - Rhionaeschna multicolor - female Hyacinth Glider - Miathyria marcella Aeschna spp. Larvae close to transformation Blue-eyed dragonfly - Pachydiplax longipennis Gray Petaltail - Tachopteryx thoreyi Dragonfly - Pachydiplax longipennis
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Odonata (Dragonflies and Damselflies)
Suborder Anisoptera (Dragonflies)
Other Common Names
Libellule (French), Libélula (Spanish)
Numbers
325 spp. in 70 genera of 8 families in our area(1); 9 families worldwide(2)
Size
body length 25-89 mm(3)
Identification
Wings usually held outstretched horizontally at rest. Hindwing is broader at base than the forewing. Male has three terminal appendages on abdomen; female has only two.(3)
Males and females often colored differently. Details important to identification include face color, eye color, color and markings on the thorax and wings, color of the pterostigma (small colored area near the front edge of the wing), color and markings of the abdomen and shape of the abdomen. Recently emerged (teneral) individuals are often pale, unmarked, and impossible to identify until they develop the adult color pattern. Some change color several times on the way to sexual maturity (within a few days); some change color with temperature, and some also change color after death.
Additional data useful for identification includes habitat (see below), season, time of day, location (especially helpful here are the checklists from the internet sources cited below), and perching habit and posture. Some species (setwings and dashers especially) typically perch with wings cocked forward and down instead of straight out.
Guide to sw. species:(4)
Range
worldwide
Habitat
Near water; species segregate by water type (shaded or sunny, still, slow-moving or swift-moving, small or broad, fresh or brackish, permanent or seasonal.) Adults of some species feed at considerable distances from water. Males of many species patrol/defend areas of water where females come to lay eggs; females may come to water only for that reason. Most species have a typical perching habit (high on or in trees, low, on the ground, etc.) and preferred shape/angle of perch (some hang from twigs, others always perch on top of them, some prefer to perch on horizontal surfaces like rocks, soil, etc.)
Season
Varies with climate: some species fly all year in the South. Others appear only in early spring, or midsummer. Generally prefer warm weather. Dragonflies are diurnal (they perch at night) but some are more active in the early morning/late evening, and some are more active in midday.
Food
indiscriminate predators on other invertebrates, including smaller dragonflies and damselflies; naiads prey on other aquatic invertebrates such as mosquito larvae(5)
Life Cycle
Females lay eggs in or near water; eggs hatch into larvae that remain in water through several moults until ready to emerge as adults. They crawl out of water onto emergent vegetation (usually), and some species can crawl many metres from water to find a safe place to emerge. As the larval skin dries, it splits, and the young adult (teneral) begins to pull itself out, a process that can take hours. Most dragonflies emerge at night or dawn, when they are less vulnerable to predation by birds than during the day. They are usually pale and unmarked; they acquire adult coloring and markings over the next several days (it can take more than a week to reach sexual maturity.) Thus in spring, when most emergences take place, you may find a lot of confusingly-marked dragonflies with intermediate coloring. (5)
Remarks
Nymphs breathe through gills in rectum; the transfer of water in and out of the rectum is used for propulsion underwater(3)
See Also
Damselflies (Zygoptera) have a more slender body, and usually hold their wings together above the abdomen at rest.
Internet References
Works Cited
1.Dragonfly Society of the Americas. 2012. North American Odonata
2.Dragonflies of the World
Jill Silsby. 2001. Smithsonian Institution Press.
3.A Field Guide to Insects
Richard E. White, Donald J. Borror, Roger Tory Peterson. 1998. Houghton Mifflin Co.
4.Dragonflies (Anisoptera) of the Southwest, by K. Biggs
5.Dragonflies and Damselflies of Texas and the South-Central United States
John C. Abbott. 2005. Princeton University Press.