Wikijunior:Bugs/Dragonfly & Damselfly
What does it look like?
[edit | edit source]Dragonflies are jewels among insects. They have shimmering wings, large reflective eyes and a long body. Their wings are very delicate and lace-like, and are usually spread when they rest.
Dragonflies have three main parts to their body: the head, the thorax and the abdomen. The thorax is just behind the head and is the power center. Its strong muscles control the two pairs of wings. Their forewings and hindwings narrow at the base and look like long tear-drops. Dragonfly legs bend, but are not very flexible. They are not made for walking. They have claws on the ends for perching on leaves and twigs. Compound eyes take up most of the head. Each compound eye has up to 28,000 separate lenses (ommatidia).
There are about 5000 species of dragonflies worldwide. About 450 species live in North America. They are large, slender insects that are up to 5 inches long. Some smaller species are less than 1 inch long.
Darners are large and fast-flying dragonflies belonging to the family Aeschnidae. They are 2-3/4 to 4-3/4 inches long. Colors are brilliant blue, green, or brown. They have large, clear wings with a span as wide as 5-7/8 inches. Darner naiads are 2 to 2-1/2 inches long with relatively short legs. Their flat lower lip lacks grasping bristles.
Green Darners belong to one of the biggest dragonfly species. They range in size from 2-3/4 inches to 3-1/8 inches. The wingspan can be up to 4-3/8 inches. They are dark greenish-brown with green thorax and blue to purplish-gray abdomen. Their pale wings have pale yellow tips. Green darners have a target-like mark on the face. Naiads can be as long as 1-7/8 inches.
Brown Darners are 2-3/4 to 3-1/8 inches long with a wingspan from 3-1/8 to 3-7/8 inches. The body is brown with 2 large, pale yellow spots on each side of the thorax. There is a brown spot at the base of each wing and a yellowish spot on the front wing margin. The four powerful wings move independently, so Brown Darners are able to fly both forward and backward. Dragonflies in Order Odonata have wings that extend horizontally to the side. They are unable to fold their wings flat against the body. Their long legs are unsuitable for walking, but are used to capture prey in flight.
Biddies belong to the Order Odonata in the Family Cordulegastridae. They are 2-3/8 to 3-3/8 inches long. Their color is brownish-black with yellow markings. Most members of this family have a very long abdomen. Their heads are wide with eyes that are slightly separated or meet at a single point. Antennas have 7 segments. Biddies are large and hairy with wings that are clear or smoky. Wings have a black spot (stigma) along the front margin. Naiads are stout and hairy with huge spoon-shaped lower lips.
Dragonflies in the Gomphidae Family are about 1-7/8 to 3 inches long. They have widely separated compound eyes. Naiads’ heads are wedge-shaped with thick antennas.
Green-eyed skimmers belong to the Family Corduliidae. They are often quite hairy. Many are brownish-black in color with a red, green, or blue metallic sheen. The abdomen is metallic green and may be long and cylindrical or flat. On the head, eyes touch each other. The thorax is hairy and wings have yellow marks.
“Downy Emerald” dragonflies (Cordelia aenea) are named for their hairy bodies and green abdomens. Their wingspan ranges can be up to 2 inches.
Small Western Gomphids are about 2 inches long and have a 4-inch wingspan. They have a yellowish face and a thorax that is black with yellow markings. The abdomen is black with a yellow tip and base. On the abdomen, there is a thick yellow stripe that narrows to a thin line. The wings are clear. Naiads are dark brown in color and about 1 inch long.
Club-tailed Dragonflies have brightly colored bodies. The thorax is yellowish with dark markings. The body has various patterns and colors combinations of black, yellow, or green. In males, the end of the abdomen is swollen, giving the appearance of a club. Females sometimes have this feature as well.
Common skimmers or “darters” usually have stout, colorful bodies and a broad, flat abdomen. Wings sometimes have dark, irregular markings with a dark base next to the body. The thorax has pale stripes on either side. Males' abdomens are pale blue and females’ are brownish yellow. Both sexes have yellow marks at the side of the abdomen.
Where does it live?
[edit | edit source]Dragonflies live near water. They inhabit open fields, forests, grasslands and woods. They are also seen in urban areas, as long as these are near water.
Brown Darners are found from Nova Scotia to Florida, west to Texas, and north to Illinois. They live at the edges of free-flowing streams. They are good fliers but do not fly very far from their home stream. Brown Darner naiads are found under stones and debris near woodland streams. Green Darners live near ponds and slow streams throughout North America. They are less common in the west. Walsingham’s Darners live in the Southwest and Heroic Darners are found from Mexico to Quebec.
Gomphid dragonflies live near streams. They can be found resting on logs, stones, and leaves or darting from one resting place to another. Sometimes they fly along roads or through woods far from the streams. They return for mating and laying eggs.
Small Western Gomphids are found near rippling streams from Nevada to Baja California and north to British Columbia.
Biddie naiads live in forest streams and cover themselves with silt. Adults can be seen flying slowly up and down streams, hovering about a foot above the water.
What does it eat?
[edit | edit source]Dragonflies are specialized hunters with large compound eyes, a freely moving head, and sharp biting mouthparts. They are very fast, catching prey with their front legs while in flight. This is called “hawking.” Hovering over plant life to catch insects is called “gleaning.”
Dragonflies eat a wide variety of insects. Their prey includes flies, midges, mosquitoes, and butterflies. They have even been known to eat hummingbirds!
Green and Brown Darners and Small Western Gomphids eat small flying insects like caddisflies and mosquitoes. Club-tailed dragonflies eat small flies, midges and mosquitoes. They use their specially-shaped legs to scoop up prey while in flight.
Dragonfly nymphs, live in water and eat worms, fleas, and insect larvae. As they grow, they feed on bigger prey like water beetles, snails, and sometimes small fish.
How does it defend itself?
[edit | edit source]They defend themselves with an advanced flight motion. Catching dragonflies is not easy. They seem to fly in 2 different directions at once. Their large mobile head and large compound eyes allow them to see motion and color. They can move swiftly through the air, darting and weaving to avoid predators.
Dragonfly wings can work independently of each other. There are joints at the base of the wings where they attach to the thorax. This arrangement lets one set of wings thrust downward while the other thrusts upward. When all four wings move together they can fly forward at up to 35 miles per hour.
Many species are mottled with different colors that act as camouflage in wooded areas near ponds and streams. Dragonfly naiads have gills and bury themselves in silt, mud, or gravel. Just the head and front legs are left out to grab prey.
What stages of metamorphosis does it go through?
[edit | edit source]Dragonflies mate in flight. Females usually deposit between 500 and 1500 eggs in or near water. Eggs hatch in 5 to 60 days depending on location and temperature. Very few eggs survive to adulthood. Dragonflies undergo simple metamorphosis with 3 stages—egg, nymph, and adult. Naiads crawl out of the water when fully grown in early spring or late summer. Males mate soon after emerging because they only live a short time as adults. Females live longer so they can lay eggs.
Darners place one egg at a time just beneath the water surface or into stems of submerged plants. Mated pairs of Brown Darners can be seen resting on lily pads while females deposit eggs. Darner naiads turn into adults in May in the north and October in the south.
Female Gomphids do not have ovipositors. Flying low over the water, they break the surface with the tip of the abdomen. Then they deposit eggs under the water surface while in flight.
Biddies lay eggs on bottoms of rivers and fast-flowing streams. Nymphs may take up to 5 years to mature, but adults of many species only live a few weeks.
Green-eyed skimmer females lay more than 2000 eggs at a time. Nymphs usually live at the bottom of stagnant water in marshes or peat bogs.
Club-tailed dragonflies mate in vegetation. Females use their tail to hit the surface and release eggs. The larval stage lasts from 3 to 5 years. Unlike other species, Club-tailed dragonflies do not have long slender larvae cases. Instead, their larvae cases are short and squat due to their unusual shape.
What special behavior does it exhibit?
[edit | edit source]Most males are highly territorial. They choose an area that has a good egg laying site. Then they protect the area by dive bombing any nearby males to force them away.
Green Darners form a “mating wheel” shape while attached upside-down to each other. After mating, the male tows the female around so she can deposit eggs. This tandem flight behavior is called “contact guarding.” It is a way for males to protect the female from advances by other males.
Some dragonfly species have a resident population that stays in the same place. Others have a migrating population. They follow the same migration paths as song birds and hawks. They stop to rest about every 3 days. Some individuals can cover 100 miles in one day. Like birds, they are able to make accurate corrections if they go off course. Nymphs of migrating species hatch and develop more quickly than those of resident species so they can begin their journey.
Dragonflies sometime swarm together on hilltops far from water. This is called “hilltopping” and may have something to do with finding a mate.
How does this bug affect people?
[edit | edit source]Dragonflies are a source of great beauty and inspiration. They have a place in folklore of many countries. Some believe they sew together fingers of people who are asleep. In the Middle Ages they were called “devil’s needles.”
In the United States, they are called darning needles, snake doctors, and snake feeders. In Japan, they are a sign of good luck, courage, and strength. If found inside the home, they are thought to be a visiting spirit. They are found in Native American art and creation myths.
Dragonflies do not harm people. Naiads and adults are beneficial, destroying huge numbers of mosquitoes. In Thailand, they are used as pest control to keep mosquitoes and other insects from rice paddies.
Scientists use dragonflies as an “indicator” species to determine if a pond or other body of water is healthy. They play an important role in preserving the balance of nature. In Italy they are called “keepers of the fish.”
References
[edit | edit source]Lockwood, S. (2008). Dragonflies. Mankato, MN: The child’s world.
McGavin, G. C. (2000). Insects spiders and other terrestrial arthropods. New York, NY: Dorling Kindersley, Inc.
Milne, L. & Milne, M. (2009). National Audubon Society Field Guide to North American Insects and Spiders. New York, NY: Alfred A Knopf.