All About Dragonflies
Is a dragonfly a fly?
No. Flies are insects with two wings. Dragonflies have four wings. However,
both flies and dragonflies are insects, meaning that they have six legs
and three body parts: a head, a thorax, and an abdomen.
Why are they called dragonflies?
The name comes from their fierce jaws, which they use to catch flies (among
other winged insects).
Where do dragonflies come from?
The dragonfly begins its life as an egg. Adult female dragonflies lay their
eggs in water. After about two weeks, the eggs hatch and an immature dragonfly,
or nymph, emerges. The nymphs are not pretty like the adults. They have
tiny wings and a large lower lip, which they use to catch their prey (often
mosquito larvae). Dragonfly nymphs live in the water. As they grow, they
molt (shed their skin). Nymphs of some species may take as long as three
years to mature.
When the dragonfly nymph reaches maturity, it crawls out of the water onto
a plant stem. Then its skin begins to split. First the head, then the thorax,
then the legs, and then the wings of an adult dragonfly emerge. Soon the
newly emerged dragonfly is able to fly. The process takes about two hours.
It takes about two days before the adult dragonfly's beautiful colors are
fully developed. Adult dragonflies live only a few months.
How long have dragonflies been around?
Dragonflies are ancient insects. They were around before the dinosaurs!
Ancient dragonflies may have been considerably larger than those we see
today. A fossilized impression of a dragonfly wing, found in a coal mine
in England, is the oldest known dragonfly specimen. This dragonfly lived
300 million years ago and had a wingspan of eight inches. The largest known
dragonfly had a wingspan of 24 inches (two feet). Today, the largest dragonfly
is found in South America and has a wingspan of slightly over seven inches.
Other than being smaller, modern-day dragonflies do not look very different
from their ancestors.
Are dragonflies like other insects?
Dragonflies and damselflies belong to an order of insects all their own,
called Odonata. Although the two are similar, damselflies are smaller than
dragonflies. In addition, damselflies can fold their wings over their backs
when they are at rest. Dragonflies can't fold their wings, so they rest
with their wings held straight out.
Are dragonflies beneficial to humans?
You bet they are! In fact, dragonflies are sometimes called "mosquito
hawk" because they catch and eat so many mosquitoes. Always on the
hunt, dragonflies consume gnats, flies, and mosquitoes--all of which humans
consider pests.
Why are dragonflies such good hunters?
Dragonflies' ability to maneuver makes them able to out-fly their prey.
But dragonflies also have the advantage of excellent eyesight. If you've
ever watched dragonflies, no doubt you have noticed their huge eyes. Each
of the two large eyes is made up of thousands of six-sided units. Together,
these smaller eyes enable a dragonfly to detect even the slightest movement.
To test this, try sneaking up and catching a dragonfly. You usually come
up empty-handed.
How can I learn more about dragonflies and other insects?
The following is a partial list of books. Check out your library and local
book store--you're sure to find many more.
Return to On the Wings of a Dragonfly
Science Bytes
University of Tennessee