Download Dragonflies of the - Science Outreach Athabasca

Life History
Most damselflies and some dragonflies (the
Darners) have well-developed ovipositors and
lay their eggs in the tissue of aquatic plants.
The rest of the dragonflies do not have this
ability and so lay their eggs on either the stems
of plants or on the water surface.
Dragonflies of the
Athabasca River Basin
Dragonflies and damselflies (Order Odonata)
are strong, brightly coloured fliers with
voracious appetites for several other insects
such as mosquitoes, midges and even other
odonates. So far 72 species have been found
in Alberta (23 damselflies and 49 dragonflies).
At least 16-40 species live in the Athabasca
River Basin. The following list of dragonflies
and damselflies is based on published records.
Origin of Dragonflies and
Damselflies
Odonata are thought to have arisen during the
Carboniferous period (250 – 300 million years
ago). Some of these ancient dragonflies were
giants, with wingspans of up to 70 cm. Over
time, the Odonata split into 2 major paths: the
dragonflies (Anisoptera) with dissimilar fore
and hind wings and the damselflies
(Zygoptera) with similar fore and hind wings.
Most Alberta forms came from the south after
the glacial retreat about 10,000 years ago.
In a week or more, the eggs hatch into aquatic
larvae that may spend several years hunting
along the bottom of the pond or stream. To
capture food, the larvae have specialized
mouthparts called a labium. They are able to
shoot these mouthparts out at high speed and,
with hooks at the end, capture prey. They are
opportunistic feeders and prey on insects,
worms, tadpoles, snails, and even small
minnows. The larvae grow until they are ready
to emerge as adults. Rates of development
depend on the amount of food and water
temperature.
Antenna (2)
Resources
Wing buds (4)
Books
Dunkel, S. 2000. Dragonflies through
Binoculars: A Field Guide to Dragonflies of
North America. Oxford University Press,
New York.
Needham, J. G., M. J. Westfall, and M. L. May.
2000. Dragonflies of North America. Scientific
Publishers, Gainesville, Florida.
Walker, E. 1953. The Odonata of Canada and
Alaska. University of Toronto Press, Toronto.
Gills
Larval
Damselfly
Larval
Dragonfly
Adults need to spend time adjusting their body
temperature. In the morning they bask in the
sun and may shiver their flight muscles to
generate enough heat to take off. When the
sun gets too hot, they seek shade, take longer
glides between wing beats, or increase the flow
of blood to their thorax to help dissipate heat.
At emergence, the larvae leave the water and
usually crawl up onto vegetation. There is no
pupal stage. The larval skin splits and the
adult emerges. The new adults need to pump
their wings full of blood before they can fly and,
during this period (up to several hours), they
are highly susceptible to predation by birds,
frogs, spiders and other dragonflies.
Odonates have very large eyes and more than
80 per cent of their brain is devoted to
processing visual information.
They have
sharp visual acuity and the ability to see under
low light levels. Their excellent eyesight is
valuable both for hunting prey and avoiding
predators.
Once airborne, dragonflies are champions of
insect flight. The wing design of the Odonata
is more “primitive” than that of most other
insects, having many veins and cells.
However, it is very efficient and they use very
little energy per unit of distance travelled.
Importance of Odonata
We can use the wings to help tell the difference
between dragonflies and the damselflies.
Dragonflies always extend their wings away
from their body. Damselflies usually fold their
wings back along their body when not in use.
Odonates are ecologically important as both
predators and prey. Amphibians, fish, birds
and other aquatic invertebrates feed upon the
larvae. One of their great benefits to us is the
adults’ voracious appetite for pest insects such
as mosquitoes, black flies, horse flies, aphids,
and grasshoppers. Odonates are also possible
indicators of water quality of wetlands.
Besides, these insects are just beautiful and
this has led to them being featured in various
commercial products, such as jewellery and
decorative items.
Westfall, M. J., and M. L. May. 1999.
Damselflies of North America. Scientific
Publishers, Gainesville, Florida.
Internet
Photographs of most Athabasca dragonflies:
http://www.ups.edu/biology/museum/
WAODphotos.html
Information on Alberta dragonflies:
http://www.ualberta.ca/staff/lfoote/research/dra
gonfly.htm
Acknowledgements
Drawings of larvae and damselfly adults from:
Morgan, A. 1930. Field Book of Ponds and
Streams. G. P. Putnam’s Sons, N.Y.
Drawings of adult dragonflies adapted from:
Needham, J., et al. 2000. Dragonflies of North
America. Scientific Publishers, Washington.
Tim Terry, Athabasca University,
prepared this brochure for:
Science Outreach - Athabasca
(http://scienceoutreach.ab.ca).
This pamphlet was sponsored by Crooked Creek
Conservancy Society of Athabasca, with assistance
provided by an Alberta Community Lottery Board grant.
June 2002