Dragonflies

Male Red-veined darter  dragonfly (Sympetrum fonscolombii) by Alvesgaspar http://commons.wikimedia.org/wiki/File:Darter_August_2007-21.jpg. GNU Free Documentation License 23/03/10
Common Blue Damselfly (Enallagma cyathigerum) photo by Alvesgaspar

A dragonfly is an insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera. It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body. Dragonflies are similar to damselflies, but the adults can be differentiated by the fact that the wings of most dragonflies are held away from, and perpendicular to, the body when at rest. Even though dragonflies possess 6 legs like any other insect, they are not capable of walking.

Dragonflies are valuable predators that eat mosquitoes, and other small insects like flies, bees, ants, and butterflies. They are usually found around lakes, ponds, streams and wetlands because their larvae, known as "nymphs", are aquatic.

Etymology

Anisoptera comes from the Greek an meaning not, iso meaning equal, and ptera meaning wings. Their hind wings are broader than their forewings.

Life cycle

Female dragonflies lay eggs in or near water, often on floating or emergent plants. When laying eggs, some species will submerge themselves completely in order to lay their eggs on a good surface. The eggs then hatch into nymphs. Most of a dragonfly's life is spent in the nymph form, beneath the water's surface, using extendable jaws to catch other invertebrates or even vertebrates such as tadpoles and fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some nymphs even hunt on land, an aptitude which could easily have been more common in ancient times when terrestrial predators were clumsier.

The larval stage of large dragonflies may last as long as five years. In smaller species, this stage may last between two months and three years. When the larva is ready to metamorphose into an adult, it climbs up a reed or other emergent plant. Exposure to air causes the larva to begin breathing. The skin splits at a weak spot behind the head and the adult dragonfly crawls out of its old larval skin, pumps up its wings, and flies off to feed on midges and flies. In flight the adult dragonfly can propel itself in six directions; upward, downward, forward, back, and side to side. The adult stage of larger species of dragonfly can last as long as five or six months.

Classification (Anisozygoptera)

Formerly, the Anisoptera were given suborder rank beside the "ancient dragonflies" (Anisozygoptera) which were believed to contain the two living species of the genus Epiophlebia and numerous fossil ones. More recently it turned out that the "anisozygopterans" form a paraphyletic assemblage of morphologically primitive relatives of the Anisoptera. Thus, the Anisoptera (true dragonflies) are reduced to an infraorder in the new suborder Epiprocta (dragonflies in general). The artificial grouping Anisozygoptera is disbanded, its members being largely recognized as extinct offshoots at various stages of dragonfly evolution. The two living species formerly placed there - the Asian relict dragonflies - form the infraorder Epiophlebioptera alongside the Anisoptera.

Dragonflies and damselflies

Damselflies (suborder Zygoptera) are often confused with newly moulted dragonflies but once a dragonfly moults, it is fully grown. There are other distinctions that set them apart: most damselflies hold their wings at rest together above the torso or held slightly open above (such as in the family Lestidae), whereas most dragonflies at rest hold their wings horizontally or occasionally slightly down and forward. Also, the back wing of the dragonfly broadens near the base, caudal to the connecting point at the body, while the back wing of the damselfly is similar to the front wing. The eyes on a damselfly are apart; in most dragonflies the eyes touch. Notable exceptions are the Petaluridae (Petaltails) and the Gomphidae (Clubtails).

Common species

Northern Hemisphere

Male Emperor (Anax imperator) by L. B. Tettenborn. http://commons.wikimedia.org/wiki/File:Ai%28loz%29.JPG. Creative Commons Attribution-Share Alike 3.0 Unported 23/03/10
Male Emperor (Anax imperator) photo by L. B. Tettenborn.
  • Emperor, Anax imperator
  • Keeled Skimmer, Orthetrum coerulescens
  • Black-tailed Skimmer, Orthetrum cancellatum
  • Common Whitetail, Libellula lydia
  • Migrant Hawker, Aeshna mixta
  • Azure Hawker, Aeshna caerulea
  • Southern Hawker, Aeshna cyanea
  • Norfolk Hawker, Aeshna isosceles
  • Common Hawker, Aeshna juncea
  • Red-veined Darter, Sympetrum fonscolombii
  • Common Darter, Sympetrum striolatum
  • Vagrant Darter, Sympetrum vulgatum
  • Yellow-winged Darter, Sympetrum flaveolum
  • Broad-bodied Chaser, Libellula depressa
  • Four-spotted Chaser, Libellula quadrimaculata
  • Scarce Chaser, Libellula fulva
  • Green Darner, Anax junius
  • Downy Emerald, Cordulia aenea
  • Blue-eyed Darner, Aeshna multicolor
  • Roseate Skimmer, Orthemis ferruginea
  • Widow Skimmer, Libellula luctuosa
  • Great Pondhawk, Erythemis vesiculosa
  • Comet Darner, Anax longipes
  • Banded Pennant, Celithemis fasciata
  • Somatochlora margarita, Somatochlora margarita

Southern Hemisphere

Black-tailed Skimmer (Orthetrum cancellatum) by Michael Apel. http://en.wikipedia.org/wiki/File:Orthetrum_cancellatum_side.jpg. GNU Free Documentation License 23/03/10
Black-tailed Skimmer (Orthetrum cancellatum) photo by Michael Apel.
  • Glistening Demoiselle Phaon iridipennis
  • Dancing Jewel Platycypha caligata
  • Mountain Malachite Chlorolestes fasciatus
  • Common Spreadwing Lestes plagiatus
  • Common Threadtail Elattoneura glauca
  • Goldtail Allocnemis leucosticta
  • Swamp Bluet Africallagma glaucum
  • Pinhey's Whisp Agriocnemis pinheyi
  • Black-tailed Bluet Azuragrion nigridorsum
  • Common Citril Ceriagrion glabrum
  • Yellow-faced Sprite Pseudagrion citricola
  • Gambel's Sprite Pseudagrion gamblesi
  • Hagen's Sprite Pseudagrion hageni
  • Hamon's Sprite Pseudagrion hamoni
  • Kersten's Sprite Pseudagrion kersteni
  • Masai Sprite Pseudagrion massaicum
  • Salisbury Sprite Pseudagrion salisburyense
  • Natal Sprite Pseudagrion spernatum
  • Orange Emperor Anax speratus
  • Common Thorntail Ceratogomphus pictus
  • Yellowjack Notogomphus praetorius
  • Rock Hooktail Paragomphus cognatus
  • Acisoma Acisoma panorpoides and Acisoma trifidum
  • Banded Groundling Brachythemis leucosticta
  • Broad Scarlet Crocothemis erythraea
  • Little Scarlet Crocothemis sanguinolenta
  • Black Percher Diplacodes lefebvrii
  • Black-tailed Skimmer Nesciothemis farinosa
  • Two-striped Skimmer Orthetrum caffrum
  • Epaulet Skimmer Orthetrum chrysostigma
  • Julia Skimmer Orthetrum julia
  • St. Lucia Widow Palpopleura portia
  • Nomad Sympetrum fonscolombii
  • Red-veined Dropwing Trithemis arteriosa
  • Navy Dropwing Trithemis furva
  • Kirby's Dropwing Trithemis kirbyi
  • Jaunty Dropwing Trithemis sticticasoy la mejor

Dragonflies in cultures

In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "devil's darning needle" and "ear cutter", link them with evil or injury. A Romanian folk tale says that the dragonfly was once a horse possessed by the devil. Swedish folklore holds that the devil uses dragonflies to weigh people's souls. Another Swedish legend holds that trolls use the dragonflies as spindles when weaving their clothes (hence the Swedish word for dragonfly trollslanda, lit. "troll's spindle") as well as sending them to poke out the eyes of their enemies. The Norwegian name for dragonflies is "Oyenstikker", which literally means Eye Poker and in Portugal they are sometimes called "Tira-olhos" (Eye snatcher). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States term "snake doctor" refers to a folk belief that dragonflies follow snakes around and stitch them back together if they are injured. The Lithuanian word "Laum zirgis" is a composite word meaning "the Lauma's horse", while in Dutch, Aeshna mixta is called "Paardenbijter" or "horse biter". In some South American countries, dragonflies are also called matacaballo (horse killer), or caballito del diablo (devil's little horse), since they were perceived as harmful, some species being quite large for an insect.

In East Asia and among Native Americans, dragonflies have a far better reputation, one that can also be said to have positively influenced modern day views about dragonflies in most countries, in the same vein as the insect's namesake, the dragon, which has a positive image in the east, but initially had an association with evil in the west.

For some Native American tribes they represent swiftness and activity, and for the Navajo they symbolize pure water. Dragonflies are a common motif in Zuni pottery; stylized as a double-barred cross, they appear in Hopi rock art and on Pueblo necklaces. It is said in some Native American beliefs that dragonflies are a symbol of renewal after a time of great hardship.

Dragonfly symbol on a Hopi bowl from Sikyatki archaeological site. http://en.wikipedia.org/wiki/File:Sikyatkibowlwithdragonfly.png. Public domain 23/03/10
Dragonfly symbol on a Hopi bowl from Sikyatki archaeological site.

They also have traditional uses as medicine in Japan and China. In some parts of the world they are a food source, eaten either as adults or larvae; in Indonesia, for example, they are caught on poles made sticky with birdlime, then fried in oil as a delicacy.

Vietnamese people have a traditional way to forecast rain by seeing dragonflies: "Dragonflies fly at low level, it is rainy; dragonflies fly at high level, it is sunny; dragonflies fly at medium level, it is shadowy".

In some parts of the world it is considered lucky to have a dragonfly land on you, even to the point of yielding seven years of good luck.

In the United States dragonflies and damselflies are sought out as a hobby similar to birding and butterflying, known as oding, from the dragonfly's Latin species name, odonata. Oding is especially popular in Texas, where 225 out of a total of 457 known species of odonates in the world have been observed. With care, dragonflies can be handled and released by Oders, like butterflies.

Images of dragonflies were common in Art Nouveau, especially in jewelry designs. They also appear in posters by modern artists such as Maeve Harris. They have also been used as a decorative motif on fabrics and home furnishings.

In Japan dragonflies symbolize "martial success," due to similarity in the sound of the word "dragonfly" and "victory" in Japanese. As a seasonal symbol, the dragonfly is associated with late summer and early autumn.

More generally, in Japan dragonflies are symbols of courage, strength, and happiness, and they often appear in art and literature, especially haiku. In ancient mythology, Japan was known as Akitsushima, which means "Land of the Dragonflies". The love for dragonflies is reflected by the fact that there are traditional names for almost all of the 200 species of dragonflies found in and around Japan. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.

Also, in Japan, amongst the Three Great Spears of Japan is one which is called the Tonbogiri, which when translated is called 'The Dragon Fly Cutter'. The spear is an important part of Japan's imperial regalia - the spear itself was once wielded by the legendary Samurai, Honda Tadakatsu. Its name is derived from the story that the blade is so sharp, a dragonfly once landed on it and was instantly cut in half.