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Order: Odonata
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Common Name Dragonflies and Damselflies
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Names
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The order Odonata is pronounced in the English form "o
do NAY ta". This scientific name is derived from a
Greek word, odon, meaning "
tooth," possibly referring to the teeth on the
mandibles or tusk-like shape of the insect's abdomen.
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Other common names for dragonflies include sewing needles,
devil's darning needles, snake doctors, horse stingers, and
mosquito hawks. The nymphs sometimes are referred to as water lizards.
The common names of "sewing needles" and "devil's
darning needles" are based on an old fable that these
insects could sew up one's ears. The term "snake doctor"
comes from a belief that dragonflies warn snakes of approaching
danger.
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Diversity
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There are about 5,000 species of dragonflies and damselflies
worldwide. It is estimated that there are 500 to 1500 species
yet to be described and named in the world. In the United
States and Canada, there are more than 410 species.
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Habitats
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Dragonflies and damselflies range from the arctic to the
tropics and are even found in desert regions where water is
present. Immature dragonflies and damselflies, called naiads,
live in water and often have preferences for a specific kind
of aquatic habitat, some preferring streams and others ponds or
lakes. Some tropical species live in pitcher plants, or
bromeliads, that gather rain water in which the naiads live.
A few species have naiads that can live on the ground under
damp leaves.
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Form and Function
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Adult dragonflies and damselflies have long, slender bodies,
large moveable heads, and two pairs of membraneous wings.
They have very large compound eyes that can see in all
directions. If the compound eye is magnified several hundred
times, each individual facet (ommatidium) is shown to be
hexagonal in shape.
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The transparent wings of dragonflies and damselflies have many
veins. Some species have beautiful color patterns. The
coloration of the male dragonfly often differs from that of
the female. Their mouthparts include large mandibles for
biting and chewing. They have small antennae that are
somewhat hairlike in appearance.
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Dragonflies and damselflies, which are usually smaller, have
wingspans of about 1-8 inches. Dragonflies are different from
damselflies in that they hold their wings out from the body
when at rest. Damselflies rest with their wings held together
over their backs.
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Dragonfly and damselfly naiads are very different in
appearance from adults. A damselfly naiads has flat, leaf-like
gills at the tip of the abdomen. These gills, which are
filled with trachea (air tubes) are used for obtaining
oxygen that is in the water. A dragonfly naiad has tracheal
gills lining its rectum inside the abdomen. (The tip of the
abdomen has three sharp projections, but these are not gills.)
The insect pulls water inside its rectum where the oxygen
diffuses through the gills into the insect's trachea.
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Life Cycle
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Dragonflies and damselflies undergo incomplete metamorphosis (egg-nymph-adult).
The eggs are laid in water or in water plants and hatch into an aquatic nymph,
or naiad. Depending on the species, the naiad stage lasts for a few weeks to
almost five years. The nymphs must shed their skin, or molt, in order to grow
in size, and they can molt 10 to 15 times before becoming mature. The mature
nymph crawls out of the water, often onto the stem of an aquatic plant, where
the adult emerges from the skin of the nymph, dries, and expands its wings, and
flys away in search of food.
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Mating of dragonflies and damselflies is peculiar in that the
mate holds the female behind the head while the female
receives the male reproductive cells. Mating pairs will stay
clasped for several hours, even flying while joined together.
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Food and Feeding Habits
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Adult dragonflies and damselflies catch and eat insects while they are
flying. These insects will eat about anything small enough for them to
handle, including flies, wasps, moths, and beetles. Adults often migrate
to an area away from their nymphal home in the water, and feed for several
weeks before returning to the pond, lake, or stream to mate and lay eggs.
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Naiads are voracious predators and feed mostly on other
insects in water, but they also can be cannibals by feeding on
other naiads of their own species. Some large naiads have been
known to feed on small fish. The naiad catch their food with
a toothed lower lip (labium) that is usually folded under
the insect's head. However, when a small insect comes near,
the nymph will shoot out its labium to grab its prey.
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Natural Enemies
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The main predators of dragonflies and damselflies are birds
which feed on both adults and naiads, and fish that eat the
naiads. There are several species of insects that can feed on
naiads such as giant water bugs (Order Hemiptera) and predaceous
diving beetles (Order Coleoptera).
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One of the most remarkable enemies of dragonflies is a
parasitic wasp, Polynema, that is among the smallest
insects known. These insects are so small that one wasp could
hide under the period at the end of this sentence. These tiny
wasps swim through the water with their fringed wings acting as
oars, locating dragonfly eggs, and laying one of their own eggs
in each dragonfly egg. When the wasp's eggs hatch, the wasp
larva eats the contents of the dragonfly eggs.
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Olympic Feats and Other Strange Facts
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Fossils of prehistoric dragonflies have been found with
wingspans of 30 inches and body lengths up to 18 inches.
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Adults of Odonata can fly backwards or forwards and even hover
like a helicopter. They can do these incredible aerial tricks
because their two pairs of wings move independently of each
other, in contrast to most other insects.
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The fastest recorded insect flight belongs to the Australian
dragonfly, Austrophlbia costalis, which can reach 36
miles per hour over short distances.
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Some dragonflies can have between 10,000 and 50,000 individual
eyes (commatidia) in each compound eye.
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The naiad shoots out its labium very fast to catch a prey, and
the forward movement requires less than three one-hundredths
of a second.
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The common green darner found in the United States, Anax
junuios, migrates north into Canada each summer. In the
fall, the offspring of these dragonflies will make their way
back to the south.
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The largest damselfly, Megaloprepus coerulatus, has a
wing spread of more than seven inches. This damselfly is
found in Central and South America.
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A dragonfly nymph can use jet propulsion to move forward very
quickly. By pulling water into the rectal chamber of its
abdomen and then shooting it out.
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The word for dragonfly in Japanese is "tombo", but
many years ago dragonflies were called "akitsu."
Japan was once called Akitsushima, meaning "The Island of
the Dragon-fly."
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The Good and the Bad
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Odonata are not considered to include pest species, although
there have been reports of some species feeding on small
minnows in fish hatcheries. People mistakenly believe that
dragonflies can sting, perhaps because a dragonfly can move
its abdomen in a stinging motion when it is held. Odonata are
incapable of stinging, but large species can bite with their
mandibles if they are held carelessly.
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Dragonflies and damselflies can be considered beneficial
because they serve a needed role in keeping populations of
other insects in control. Adult Odonata can prey on
mosquitoes and other flies.
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In some cultures, Odonata become meals for man. People on
some Pacific Island have been reported to catch dragonflies
with long poles smeared at the top with a sticky substance.
The trapped dragonflies are cooked with onion and other spices
and eaten. In some parts of eastern Asia, dragonfly nymphs are
roasted and are said to taste like crayfish.
Odonata in Human Culture
has other references for the role of dragonflies and damselflies
in various cultures.
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Taxonomy--Families of North American Odonata
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Aeshnidae (darners)
Corduliidae (green-eyed skimmers)
Cordulegastridae (biddies)
Gomphidae (clubtails)
Libellulidae (common skimmers)
Macromiidae (river skimmers)
Petularidae (graybacks)
Calopterygidae (broad-winged damselflies)
Coenagrionidae (narrow-winged damselflies)
Lestidae (spread-winged damselflies)
Megapodagrionidae
Platystictidae
Protoneuridae
Pseudostigmatidae
Synlestidae
Odonata of North America has a list of species of North American Odonata.
For an extensive list of Odonata Web sites, go to the Links Component of the module.
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Selected References
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Corbet, P. S. A Biology of Dragonflies. Witherby, London, 1962.
Dunkle, S. W. Dragonflies of the Florida Peninsula, Bermuda and the
Bahamas. Scientific Publishers, Gainesville, FL, 1989.
Hutchins, R. E. The World of Dragonflies and Damselflies.
Dodd, Mead, & Co., New York, 1969.
Needham, J. G., and Westfall, M. J. A Manual of the Dragonflies of North
America (Anisoptera). University of California Press, Berkeley, 1955.
Westfall, M. J., and May, M. L. Damselflies of North America.
Scientific Publishers, Gainesville, FL, 1996.
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Photo Credits
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Dr. Ross E. Hutchins (Deceased)
Mississippi Entomological Museum
Widow Skimmer Dragonfly
Calopteryx Damselfly
Compound Eye of Calopteryx Dragonfly
Magnification of Compound Eye
Wing Veins of a Dragonfly
Sexual Dimorphism in Male (Left) and Female of Plathemis lydia
Naiad of a Dragonfly
Mating Pair of Dragonflies
Labium of Damselfly Extended
Parasitic wasp (Polynema), on Dragonfly Eggs
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