Find dragonflies information at Animal Diversity Web
Immature dragonflies have six spindly legs, and a body that is only a few times longer than it is wide. They have two fairly big eyes. Some of their mouthparts are modified to shoot forward and grab prey. They breathe water through gills in their abdomen, and can squirt this water out fast to give themselves a quick jet-propelled movement. Adult dragonflies are easy to recognize. They have long thin bodies, very large eyes, and they hold their 2 pairs of wings out flat on either side. Their legs sometimes have many long stiff hairs. Immature dragonflies are usually brown or greenish, and sometimes have algae growing on them. Adult dragonflies can be very colorful, some are red, blue, yellow, or green.
Dragonflies are found all over the world. In Michigan there are 114 species
Immature dragonflies live in freshwater. They are most abundant an diverse in slow-moving freshwater that has no fish (small streams and ponds) but can be found in many shallow freshwater habitats. Adult dragonflies often stay near water, but sometimes travel away from water while hunting or on migration. They are fast fliers, so they tend to hunt in open areas, not in thick trees or other vegetation.
Dragonflies hatch from eggs in freshwater, and spent at least a few months (sometimes several years) as aquatic predators. As they grow they molt (shed their whole skin at once) many times. Once they are big enough, they crawl out of the water and the adult stage emerges from the skin of the nymph. Once they have transformed into the winged adult stage, the stop growing.
Most dragonfly species spend the winter as nymphs in the water, but some migrate south, and spend the winter as adults. In few species that lay their eggs in the late summer or fall, the eggs don't hatch until spring. Dragonflies emerge from the water in the warm months of spring or summer.
spring or summer
After mating, female dragonflies lay dozens or hundreds of eggs. Different species place them in different places in or near freshwater. Some put them in the water, some in plants over the water, some in mud or algae at the edge of the water.
Dragonflies live for months at least, and some live for several years as aquatic larvae before emerging and living for a few months as adults.
Dragonflies need sunny warm weather to fly, usually the temperature must be over 65°C. If it is too cold or wet, they hide in vegetation. Adult male dragonflies often establish territories along the edges of ponds or streams. They only defend the territory against other males of their species. Some large dragonfly species migrate south to warmer climates at the end of the summer. Their offspring may then migrate north the following year.
Adult dragonflies communicate visually much more than most other insects. Males fight aerial duels for territory, displaying their size and speed to each other. Mating pairs probably communicate by touch, possibly chemically too
Dragonflies in their aquatic stage eat many kinds of small animals: aquatic insects, tadpoles, small fish, and other invertebrates. Adult dragonflies eat flying insects, especially mosquitoes and other true flies, but also aphids, smaller dragonflies, damselflies, and just about any other insects they can grab.
Immature dragonflies avoid predators by hiding, and by jetting away if they have to. Adult dragonflies avoid predators with their quick and agile flight, and hide in vegetation when it is too cold to fly.
Dragonflies are sometimes the top predators in ponds with no fish. Adult dragonflies help control populations of mosquitos and other flies.
Dragonflies help control populations of biting flies like mosquitos.
controls pest population.
Most dragonfly species are abundant and common, but a few use special habitats as immatures, and they are at risk because their habitats are in danger.
There are some old stories about dragonflies stinging or stabbing people. They are not true. Dragonflies are totally harmless to people.
George Hammond, Animal Diversity Web, University of Michigan Museum of Zoology