| Size |
12.7 to 25.4 mm, ½
to 1 inch |
| Habitat |
Generally, dragonfly larvae are bottom
dwellers. Many species live in areas of standing water such as permanent or temporary
ponds, lake edges, swamps and marshes. A few species live in the soft sediments, bank
vegetation or bank debris of streams. When disturbed, dragonfly larvae can move quickly to
safer habitats by expelling water out their rectal chambers. Some species are
excellent swimmers and use their rectal chambers as jet propulsion systems. |
| Reproduction |
Dragonflies are a hemimetabolous order with all
species having aquatic larvae. The dragonfly life cycles can take up to four years to
complete! Adults disperse and feed for a week or more before returning to breeding sites.
At the breeding sites, a male chases other males out of his territory while trying to
capture a female when she has entered his territory. After he captures a female, mating
occurs. Soon, the female lays eggs one by one inside plant tissues that are below, at or
above the surface of the water. Eggs can also be laid one by one or in a large mass on
plants, debris or other underwater structures, or laid on the surface of the water (they
later sink to the bottom). After the larvae hatch, they crawl out of the water and dry
off. Once their exoskeleton dries and cracks, the adult climbs out of the
exoskeleton and flies away in search of a mate. Generally, the adult stage only lasts up
to few weeks. |
| Feeding |
Dragonfly larvae are predators that mostly feed
on other small invertebrates, shrimp, small fishes and larval amphibians. As a result,
dragonfly larvae are key predators in invertebrate communities. Adults are also predators
feeding on mosquitoes and other flying insects, such as black flies (Simuliidae) and horse
flies and deer flies (Tabanidae). |
| Predators |
There are many potential predators at all stages of life.
Larvae are prey to larger predatory insects, fish, frogs, turtles and birds. When larvae
emerge from the water to metamorph into adults, they are still soft and cannot fly
well. As a result, newly emerged larvae are vulnerable to birds and frogs. Birds and frogs
will also feed on larvae and adults when they become concentrated into small pools as a
result of a drought. Adults flying into a spider’s web may become trapped and food
for the spider. |
| Description |
Dragonfly larvae are easily distinguished from other insect
larvae. Larvae are elongated with a hinged labium, large eyes and short antennae.
Some species of dragonfly larvae are covered with coarse "hairs". Larvae have
three triangular-shaped pointed appendages at the end of the abdomen. Colors typically
reflect their surrounding habitat (mostly brown). Gills are found inside the rectal
chamber. Movement of water in and out of this chamber greatly enhances respiration
allowing dragonfly larvae to reside in areas of standing water where dissolved oxygen
levels may be less suitable to other aquatic organisms. Coloration in adults ranges from
brown and black to green, red and blue. Adults do not resemble larvae in that they have
very elongated abdomens and two pairs of large veined wings. Adult dragonflies can be
distinguished from adult damselflies in two ways: 1) adult dragonflies have much larger
and thicker bodies than adult damselflies; and, 2) adult dragonflies hold their wings
horizontally in relation to the abdomen when at rest, while adult damselflies hold their
wings vertically in relation to the abdomen when at rest. Neither insect can fold its
wings. |
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