Forest Preserve District of Cook County (Illinois)
Nature Bulletin No. 299-A March 23, 1968
Forest Preserve District of Cook County
Richard B. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation
****:DRAGONFLIES AND DAMSELFLIES
Few creatures are more fascinating to watch than those graceful
airplane-like insects which patrol the ponds and streams -- the
Dragonflies. In the world of insects they excel in speed, aerial
acrobatics and ability to hover seemingly motionless in mid-air.
Zooming and darting like fighter planes, the four long narrow wings of
the dragonfly move so fast that they blur and buzz like miniature
propellers. Their smaller relatives, the Damselflies, have a lazier
flapping flight.
About 2700 species of these sun-loving insects are known, mostly in
warmer climates where their young grow up in freshwater lakes, ponds
and streams. The bodies of most kinds are vividly colored -- red, blue,
green or yellow, with spots or stripes on their beautifully veined
cellophane-like wings -- the males usually having more brilliant
metallic hues than the females. The adults eat enormous amounts of
mosquitoes, gnats and other insects which they scoop out of the air in a
"basket" formed by their legs and "chest", like a boy catching a
football. They chew and swallow their prey, either while on the wing or
as they sit alert for another victim, turning their heads from side to side.
With a pair of great jeweled eyes covering over half of the head, and a
long stream-lined abdomen, they look like some strange flying dragon
belonging to the dim past. This is not so far-fetched. They are among
the oldest known insects, and fossil dragonflies with a wingspread of
two feet have been found in rocks of the Coal Age.
The females often flying "tandem", with the male in front to help break
the surface, place their eggs underwater. Other kinds lay them in long
strings on aquatic plants. These hatch into tiny six-legged young called
nymphs which, after feeding underwater for several months or more,
and ten to fifteen molts of their skins, reach full growth. Then the
nymph crawls from the water onto some rock, twig or grass blade, the
skin splits down the back, and a pale much-rumpled adult climbs out.
For protection this usually happens at night. In an hour or so the wings
unfold and the adult is ready for its brief life of a few months.
Damselflies can be distinguished from dragonflies because they are
more slender and when at rest, instead of holding their wings straight
out from their sides, like an airplane, they fold them together over the
abdomen, like a butterfly. Their young, too, are distinctively different.
Dragonfly nymphs are stocky awkward creatures that lie in wait for
small swimming animals -- water fleas, mosquito wigglers, worms,
tadpoles, and even young fish -- which they grab with a long jointed
lower lip that has a spoon-like tip, Still more strange, they are jet-
propelled. They can fold their legs and dart forward by squirting water
from the gill chamber that fills most of the abdomen. The damselfly
nymphs, on the other hand, are more slender, have grasping jaws, and
have three oar-like gills on the tail end which enable them to swim like
fish.
The high-flying Big Green Darner has a bright green head and thorax,
and a four-inch wingspread. It is our largest common dragonfly and the
"devil's darning needle" that is supposed to sew up the ears of boys who
play hooky. Locally, we have smaller species called Amber Wing,
White Tail and Ten Spot, that skim the surface of the water. Some of
our damselflies are named Bluet, Ruby Spot and Black Wing but
youngsters call them all "snake doctors" or "snake feeders".
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