In this KET video segment from Kentucky Life, learn about dragonflies and damselflies. See these beautiful insects in flight, and learn about their habitats from a biologist.
Dragonflies and damselflies are insects of the scientific order Odonata (o do NAY ta), derived from the Greek word for “tooth.” This name may refer to the tusk-like shape of their bodies or to their mandibles that look like teeth. The mandibles are actually chewing mouth parts that help the insect devour the prey it catches in flight. Dragonflies will eat just about anything small enough for them to overpower. This includes flies, mosquitoes, wasps, moths, and beetles. They don't bite humans nor do they sting. In fact, they help humans by eating other insects considered pests.
Dragonflies and damselflies have managed to survive virtually unchanged for 300 million years but they are dependent on good-quality water ecosystems for their survival. Their larvae begin their lives in the water. Adults drop their eggs onto aquatic plants or directly into the water of small streams, creeks, or ponds. The nymphs that hatch from the eggs are carnivores that feed on other aquatic organisms, including smaller nymphs. The nymphs of some species can live in the water as long as four years. In the water the nymphs are vulnerable to water pollution and lack of oxygen. By monitoring the nymph population, humans can determine the health of the water ecosystem. If all of the nymphs disappear, it is an indication that the water is not healthy for many species.
When the nymph is completely grown it will crawl up the stem of an aquatic plant, shed its exoskeleton, and emerge as an adult dragonfly. The adults live for about two months, hunting, eating, and even mating on the fly.
Dragonflies and damselflies both have the insect characteristic of three distinct body parts—head, thorax, and abdomen—with six jointed legs attached to the thorax. They both have large compound eyes that can see in all directions, small antennae, and transparent veined wings. One way to tell them apart is that dragonflies' eyes are in front of their heads and usually touch, while damselflies' eyes are on opposite sides of their heads. Also, damselfly forewings and hindwings are about the same size while dragonflies' hind wings are larger than their forewings. In addition, when damselflies are at rest, their wings are parallel to their body. Dragonflies at rest keep their wings perpendicular to their bodies.
The wings are perhaps the most distinctive feature of dragonflies. Though they only flap their wings about 30 beats per second, as opposed to a bee’s 200 bps, they are excellent fliers. Because they have two pair of wings moving independently of each other, dragonflies are able to fly backward or forward, hover like a helicopter, and do incredible aerial tricks to outmaneuver both their prey and predators. These maneuvers are part of the magic that makes the elusive dragonfly mesmerizing to watch and stronger fliers than damselflies.
To learn more about dragonflies that live in another region, check out Primitive Insects of the Congaree Swamp.
To learn more about metamorphosis, the process by which an animal's body dramatically changes form on its way to becoming an adult, check out Metamorphosis: Change of Plans.
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