All about dragonflies and damselflies

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Dragonflies and damselflies are among the most fascinating and beautiful insects on earth. They’re quite ancient, with some fossils dating back to the Permian Period around 285 million years ago. Fossils similar to dragonflies go back to the Carboniferous Period 300 million years ago,¹ which is roughly 40 million years before the first dinosaurs appeared. One of these extinct species measures over 28 inches from wingtip to wingtip! The largest of today’s dragonflies measure no more than 7-1/2 inches.

Dragonflies and damselflies belong to the order Odonata (oh-doe-NAW-tuh), a name which comes from the Greek odonto for tooth and is a reference to their mouthparts, which are designed for chewing. There are 5,746² classified species of Odonata in the world, with roughly half being dragonflies and half being damselflies. Dragonflies and damselflies are found on all continents except Antarctica. About 450 Odonata species in 11 families inhabit North America; two-thirds of them are dragonflies.

Odonata is divided into two suborders: Dragonflies are in Anisoptera (an-iss-OP-ter-uh), which is from the Greek for “different wings,” because the hind wings are a bit larger than the forewings. Damselflies, whose wings are all the same size, are grouped in Zygoptera, which means “same wings.”

Dragonflies handled carelessly will try to bite humans and the larger ones can deliver a painful pinch. However, neither dragonflies nor damselflies have stingers and they’re otherwise harmless to humans. Not only are they harmless, but they benefit us by being awesome predators who consume prodigious amounts of nuisance insects like gnats and flies. And, mosquitoes — giving rise to the name some people call them — “mosquito hawks.” Dragonflies feed on anything small enough for them to snatch and hang on to, including other beneficial insects like bees and butterflies, and even tiny animals. Odonata larvae feed on anything small enough to catch and chew up, such as worms, water beetles, mosquito larvae, fish. In spite of the exceptional ability of Odonata to catch prey, they are themselves heavily preyed upon, especially in their immature stage.

Physical characteristics
Adult dragonflies and damselflies refuse to be ignored. First, there’s their curiously long body. Even the smallest North American species, the Citrine Forktail (Ischnura hastata), is about an inch long and the largest, probably the Giant Darner (Anax walsinghami), has a wingspan of about 3 1/2 inches.

Females are usually less colorful than males. But most dragonflies and damselflies practically scream, “Look at me,” in their bright body colors—blue, lavender, green, bronze, scarlet, pink, red or yellow, sometimes even a blazing iridescent. They wear stripes and lines and bands or spots. Even those burdened with earth tones may be brightened with splotches of color. Sometimes even their otherwise transparent wings have spots, bars or bands to add a jaunty look to their ensemble.

Dragonfly eyes touch in the center. Damselfly eyes do not. (© l: Phil Date; r: Piotr Adamski)

L: Dragonfly eyes touch in the center (© Phil Date); R: Damselfly eyes do not touch (© Piotr Adamski)

Their eyes — so huge they cover most of the face — reflect light in shades of bright blue, green, red, yellow-orange, brown or black. The eyes aren’t merely pretty, they’re pretty perfect: They’re compound, with 20,000 to 30,000 facets, called ommatidia (ah-muh-TID-ee-uh), which gives them nearly 360 degrees of vision. Video of damselfly grooming its face

Odonates also have three simple eyes, or ocelli (oh-CELL-ee), on their face, which are sensitive to light intensity. Color defines the rest of the face, too. Some are white-faced or black, but many are green, red, yellow or blue. Odonates’ wings are narrow and crisscrossed with veins that help give them strength. All four wings of both groups usually have a “stigma,” which is a patch of color on the front edge. There are some differences in the wings of the two groups, however: Dragonfly hind wings are slightly broader than the forewings, while damselfly wings are all the same size. Dragonflies at rest hold their wings horizontal and at right angles to their body.

Almost all damselflies, on the other hand, rest with their wings usually upright and together, in line with their body, and their wings are narrow at the base. The one exception is the Lestidae family, which spread their wings more like dragonflies.

Damselflies are weaker fliers than dragonflies, although still very fast and agile. Prey are doomed when an Odonate targets them: Their wings can beat 20 to 45 times a second and do it separately, giving them incredible speed and agility. Especially dragonflies. They’re the aerobatic champions of the insect world. They can fly at bursts up to 35 miles per hour, turn 180 degrees in an instant, jet straight up or dive straight down and hover briefly. They can even fly backwards. What these insects want, they get!

Some dragonflies migrate southward as winter approaches. Some populations of the Common Green Darner, Anax junius, are known to migrate round trip. Radio-tagged individuals have been tracked flying to the northern U.S. and southern Canada in the spring after emerging in the southern U.S. Their offspring then made the return trip in the fall. Dragonflies migrate like birds

The Odonate’s head perches at the end of a “neck” and it can swivel. The head is almost all eyes and mouthparts. Damselfly eyes are positioned wide apart, forming a bulge on each side of the head, whereas dragonfly eyes are closer together and often touch in the middle. Odonates have a pair of antennae (an-TEN-ee), but they’re short and thin, rather inconspicuous. The legs are long and bristly, which helps them hold onto large prey.

(WikipedianProlific / Wiki; cc by-sa 3.0)

(WikipedianProlific / Wiki; cc by-sa 3.0)

Damselflies are usually smaller than dragonflies and have a very slender, cylindrical abdomen. A dragonfly’s abdomen is also long, cylindrical and slender, but it’s heavier-looking.

The males have four appendages at the tip of the abdomen. Two of them are claspers, used to hold onto the female during mating. The other two are cerci (SIR-sigh; singular, cercus). Claspers are species specific. Females have two cerci, along with a conspicuous egg-laying organ called an ovipositor (oh-vuh-POZ-uh-ter) at the tip.

Habitat
Dragonflies and damselflies will visit saline water, but most are found wherever there’s freshwater — be it a stream, pond, lake, river, bog, marsh, wetlands or small backyard water garden. Even springs and lakes in the desert have Odonates. Some species like streams moving through coniferous or deciduous forests, while others choose habitats in grasslands or meadows. Certain species like still or slow-moving water, while others like faster water. At any time of day, you’re likely to see one species or another. Some, usually damselflies, fly close to the ground in their hunt for prey.

Common Whitetail Dragonfly (Plathemis lydia) male basking in the sun. (WW)

Some Odonates like to perch on twigs or stalks that are sticking out of the water. Others prefer shady woodlands and still others like grassy areas. Like butterflies, Odonates must warm their wing muscles before taking flight. So, look for them to be perched motionless on stems and twigs, basking in the heat of the morning sun, or even shivering their wings to warm them up.

Food sources
The beauty of dragonflies and damselflies doesn’t touch the insect world lightly. Both as immatures and adults, Odonates feed voraciously on anything they can catch and hang on to, be they insects, tadpoles, small fish and even other dragonflies and damselflies. There’s even the occasional story of a hummingbird being captured. Dragonflies usually hunt on the wing, snatching small prey directly into their mouth and the bigger ones with their legs before moving them to their mouth. Damselflies are more likely to feed on insects they find on vegetation.

Life Cycle
Odonates undergo incomplete metamorphosis — from egg to nymph to adult — through a process called hemimetabolism. Beginning as a fertilized egg (first stage), the baby odonate hatches into his second stage. Now called a nymph (NIM-f) or naiad (NAY-ud), it looks a little bit like its parents, but lacks wings. It eats and grows larger until it reaches the third stage, adulthood. Along the way, its body is completing its development and it molts several times — from 8 to 17 times, depending on the species. With each molt, it looks more and more like its parents. Its last molt reveals its full-sized, winged, sexually mature, adult body.

Damselflies (Calopteryx splendens) mating. (Quartl / Wiki; cc by-sa 3.0)

Damselflies (Calopteryx splendens) mating. (Quartl / Wiki; cc by-sa 3.0)

Dragonflies and damselflies are unique in that the male has two sets of sexual organs. It isn’t known why they have evolved this way, but the “primary organ” is on the ninth segment of the abdomen and the “secondary organ” is located on the ventral side of the second segment. In mating, a male first grabs a female by her prothorax or the back of her head with his two claspers and holds on. Just before copulation he curls his body so he can transfer a packet of sperm directly from the primary organ to the secondary. The female in turn curls her body around until her sexual organs come in contact with the male’s secondary organs. This forms a shape that’s unique in the insect world and referred to as the “wheel position,” but it really looks more heart-shaped than round.

Damselflies mate while perching, but dragonflies usually start mating while in flight and might then settle on a perch to finish. Sometimes after copulation the couple separates their genitals but stays attached in a “tandem position” with the male continuing to clutch the female’s prothorax until the female is ready to deposit her eggs. It’s speculated he does this to keep the female from mating again, thereby ensuring his sperm fertilizes the eggs. (The male dragonfly is really competitive about this—he’s known to scoop out of the female’s organ any semen she may still be carrying from a previous sexual encounter.) Some dragonfly and damselfly species stay in tandem during the actual egg laying. With some, the male merely guards the female from other males as she lays her eggs.

Females don’t necessarily lay their eggs immediately and may lay several thousand eggs before their life ends. Some species lay their eggs in the water and others lay them in the stems of aquatic plants. Some eggs overwinter in water, but most species hatch out in one to eight weeks. The hatchlings are called nymphs (NIM-f) or, oftentimes, naiads (NAY-ud). They usually spend three or four weeks living in water as nymphs, but some take longer.

Nymphs don’t have their parents’ beauty. They’re rather homely, six-legged, oval-ish, wingless, brown or green things. Nature writer, Terry Krautwurst, describes them* as armored-looking creatures who could have been designed by the creators of the movie Alien. They’re certainly as lethal as the Alien, crawling around underwater consuming everything possible. Not only that, but attached to their head is a rather creepy labium (lower lip) that functions something like a human arm with an “elbow” mid-way. At the tip are claws. This lip is kept folded underneath the head and thorax until suddenly, in a fraction of a second, faster than our eyes can see, it’s thrust forward and back, snatching a prey and pulling it to the nymph’s mouth. (This site has an animation of this, plus many interesting short videos of Odonata behavior.)

Dragonflies can be distinguished from damselflies by the gills. A dragonfly’s gills are hidden in his rectum. Damselflies, on the other hand, have three long, leaf-like gills extending from the tip of their abdomen.

Nymphs, depending on the species, shed their exoskeleton eight to 17 times to accommodate their growing body. With each molt their body shows a little more maturity, until finally it’s ready to breathe air, the wings are eager to fly and the sexual organs are ready for mating. The nymph crawls out of the water and clings tightly to a support — a plant stem, twig or rock — then molts for the last time.

A dragonfly after last molt clings to old skin, waiting for wings to dry. (Simon Coomber / StkXchng; cc by 2.0)

Its skin splits down the back and, with great effort, it begins working his way out. (The discarded skin is called exuvia and you might find one still stuck to a stem long after the Odonate is gone.)

These are exciting minutes, as we wait to see the color-drenched adult completely emerge. But, wait! This can’t be right: Its bright body colors aren’t there. It’s pale and unremarkable. And its wings, well, they’re short and hanging down, looking limp, like it’s starting its terrestrial life in a state of depression. What’s going on?

First of all, like butterflies and moths, its wings won’t be functional until it pumps them up with blood it’s holding in its body cavity—this stretches them out to their full size and gives them rigidity. Then they must dry. It’s a precarious, largely defenseless time for the new adult; it’s easy pickings for any predator passing by.

After a brief drying time, it might be able to clumsily, slowly, lift itself skyward, but an escape would largely depend on luck. Once its wings are dry, however, it will sleekly lift itself skyward, looking for all the world like it’s done it hundred times before. Now it’ll be much harder to catch.

Over the next few days, it’ll feed heavily and its body color will develop. Then, dressed in its best, it’ll turn its mind to matters of courtship and mating. If it’s a territorial male, he’ll stalk out an area near water and defend it against entry by other males. Females, of course, are welcomed in. If it happens to be a non-territorial species, males may join several other males in pursuit of a single female. Many species of females stay away from breeding areas until they’re ready to mate or lay eggs.

Adults can live up to about two months or so, but probably average less because of predation by birds, fish, frogs, turtles, spiders and other insects. Some species, counting from egg through adulthood, live several years, with most of it spent in the nymph stage. Adults don’t survive in winter. Dragonflies and damselflies spend their winter as eggs or nymphs in unfrozen water.

Predators
Dragonflies and damselflies are especially vulnerable to predators while they’re in the egg or nymph stage. Once they become airborne they’re harder to catch. In the water, they’re preyed on by fish, water beetles, frogs and other carnivorous water species. Out of the water, they’re prey for whatever can catch them unaware, including songbirds, waterfowl, large insects (such as robber flies) and spiders.

*Top photo: Flame Skimmer Dragonfly, Libellula saturata. (Kathleen Christiansen / Flickr; cc by 2.0
¹Mother Earth News Magazine, Sept. 8, 2006, pg. 27
²Source: ITIS Catalogue of the Odonata of the World, 2011

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