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The incubation period can be several days if conditions are favorable
or as long as several months under harsher conditions. The larva (also called
nymph or naiad) hatches from an egg about 1/10th of an inch long. It is nourished
for a few days by a yolk. Then it must begin to catch food on its own. The
larva spends most of its early life hunting for food. Since is is primarily aquatic
it does so in water.
Larvae look entirely different from adult forms but share the same
body divisions - head, thorax, and abdomen. The
lower lip (labium) can be extended and retracted at high speeds to bring prey directly
into the mouth which is flanked with slicing mandibles. A larva will eat anything
from mosquito larvae to small fish, frogs and toads, and even other larvae.
Dragonfly and damselfly larvae occupy all types of aquatic habitats, some even use
tree cavities! Some larvae can alter the color of their bodies to match their surroundings.
In this way they are more effectively camouflaged and less likely to be seen by
enemies. They are often classified according to their behavior:
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Climbers such as darners can be seen climbing in and out of
submerged weeds or grasses stalking their prey.
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Sprawlers are slow moving and usually have flattened, hairy
and drab colored bodies. They usually lie flat on the mud
covered with algae with their long legs stretched out watching for prey to come
their way.
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Burrowers such as clubtails and spiketails have almost flattened
bodies and can usually be found lying in sand or other sediments with only their
eyes and tip of the abdomen exposed at the sand surface. All burrowers
are dragonflies (no damselflies).
Damselfly larvae have three feather-like gills located externally
at the end of the abdomen. Dragonfly larvae do not have these protruding gills.
In both groups, the gills play a major function in locomotion, enabling the larvae
to catch prey and escape from predators at amazingly fast speeds.
The developing larva must repeatedly shed its outer shell in order
to grow larger, each stage is referred to as an
"instar".
Complete development may involve as many as 20 instars and take several years, depending
upon the species and environmental conditions.
Cold weather and lack of food can delay the larva's development.
During cold weather it may remain in a semi-dormant state until spring when food
and warmth are plentiful. In northern areas, some larva may remain in the water
for many years, but where climates are warm, development is usually quicker.
As the time approaches for the final instar or molt, the internal
organs of the larva change into those of an adult. Some of these changes can
be seen: an enlargement of the compound eyes, swelling of the wing sheaths, and
retraction of the muscles within the labium. Shortly before emergence the
larva ceases to feed and moves closer to a site where it can emerge. Finally the
gills no longer work under water and the larva must surface.
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