DRAGONFLIES (ODONATA) OF BRITISH COLUMBIA
Black Petaltail (Tanypteryx hageni), photo by Ian Lane
R. A. Cannings and G. G. E. Scudder
Copyright © 2005 - All rights reserved
Extracted from the forthcoming publication The Insect Families of British Columbia
Visit the atlas pages for the Odonata of BC
Description (draft only)
the insect order Odonata contains both the groups of insects
known in English as the dragonflies and damselflies, following
common usage we also use the name “dragonflies” to
refer to the order as a whole. The Odonata contains about 5000
named species and 23 families world-wide. It is predominantly
tropical in distribution and is not as diverse at higher latitudes.
Odonata and their ancestors are some of the most ancient of insects.
They have many primitive features, but also possess many specializations
that reflect their aerial and predatory lifestyle. The huge compound
eyes and minute, hair-like antennae emphasize their visually
oriented behaviour. The order contains two suborders in British
Columbia: the Zygoptera (damselflies), the Anisoptera (dragonflies).
Damselflies are slimmer, often smaller, and usually fly more
slowly than dragonflies. At rest their equal-sized wings are
usually held together above the body. Zygoptera means “joined
wings”. Dragonflies are robust, often fast-flying, with
the hindwings broader than the forewings: when perched they hold
their wings out away from the body. Anisoptera means “unequal
Pacific Forktail (Ischnura cervula), photo by Dave Ingram
are 10 families, 27 genera and 87 species known in the province.
They range in size from the small Ischnura perparva Selys
and Nehalennia irene (Hagen) (wingspans as little
as 25 mm) to the large Anax junius (Drury) and Cordulegaster
dorsalis Hagen (wingspans to 110 mm), which are among the
largest of our insects.
are large and abundant insects and, because of this, the order
forms one of the predominant groups in standing freshwater communities
in British Columbia. In the mountains of western Canada, species
are less abundant in running water than they are in standing
water habitats, presumably because the former are often cold,
originating in mountain snows. Dragonflies live around most types
of fresh water. Certain kinds prefer lakeshores, others are found
only along streams, or around springs and in peatlands. Ponds
and marshes rich in aquatic vegetation support the most species.
Canada Darner (Aeshna canadensis ), photo by Sylvia Letay
have two pairs of long, membranous wings patterned with numerous
cross-veins. Although dragonflies cannot fold their wings flat
over their backs (an ancestral condition they share with mayflies),
unlike most insects they can work their four wings independently.
This produces in extremely agile flight, making the insects superb
aerial predators. Their prey is a wide range of flying insects,
and is usually captured in flight with the dragonfly’s
spiny legs. Despite tales to the contrary, dragonflies do not
bite or sting people. Adults are often colourfully patterned,
and exhibit a wide variety of readily observed behaviour. Mature
males patrol the breeding habitats, aggressively searching for
mates, and may, like birds, defend a territory against other
males of the species. These territories limit aggression and
prevent undue disturbance of egg-laying females. Sometimes in
crowded situations group territories with dominance hierarchies
he is ready to mate, a male grasps a female by the front of the
thorax (damselflies) or by the top of the head (dragonflies)
with the appendages at the tip of the abdomen. The female loops
the end of her abdomen up to the base of the male’s abdomen
where the sperm is stored and transferred via the unique secondary
genitalia. The Odonata are the only insects that mate in this
Cardinal Meadowhawk (Sympetrum
illotum), photo by Dave Ingram
female lays the eggs once they are fertilized. All damselflies
and some dragonflies (mainly the Aeshnidae) have a knife-like
egg-laying structure called an ovipositor, at the tip of the
abdomen. They lay their eggs in plant tissue of various sorts.
Competition for mates is usually fierce, and male aggression
can prevent females from laying their eggs. Females ovipositing
alone are usually secretive. In many species, the male often
retains his hold on the female while she lays her eggs, guarding
her from other males who may attempt to mate with her. Some damselflies
actually crawl below the water surface to escape the attentions
of males, remaining there for over an hour to lay their eggs.
The large stream-dwelling Cordulegaster has a spike-like
ovipositor that drives eggs into the mud and sand of the streambed.
Other species lacking ovipositors usually just dip the tip of
the abdomen into the water and wash the eggs off, and the eggs
sink to the bottom.
aquatic larvae are predacious and are armed with an enormous
hinged labium, sort of a lower lip, which is used as an extendible
grasping organ for capturing prey. This type of labium is unique
to the Odonata. Larvae are voracious, eating small aquatic insects,
crustaceans and even fish. Anisopteran larvae pump water in and
out of the rectum, which is lined with gills. This pump is also
used as an escape mechanism – if a jet of water is forced
out of the rectum, the larva speeds away, jet-propelled. Zygopteran
larvae have three leaf-like gills at the tip of the abdomen.
can be categorized according to their feeding behaviour. Climbers
(Zygoptera, Aeshnidae) are streamlined stalkers that live in
submerged vegetation. Sprawlers (Macromiidae, Corduliidae and
Libellulidae) lie in ambush on the bottom mud and detritus. Burrowers
(Gomphidae, Cordulegastridae) cover themselves with sand and
mud and await their prey. Larvae moult 10 to 15 times as they
grow. When fully grown, the larva crawls out of the water up
a plant stalk or some other support. The skin on its back splits
open and the adult dragonfly emerges, expands and dries. The
empty larval skin (exuvia) remains as a reminder of the larva’s
and many dragonflies, develop rapidly. For many species in British
Columbia the life cycle takes about a year. Lestes and
some Sympetrum species overwinter as eggs, hatch in
the spring and emerge as adults in the summer. Others overwinter
as larvae and emerge the following spring or summer, although
probably in some species under certain conditions, the larvae
overwinter two years. However, in the larger dragonflies, such
as Aeshna or Somatochlora, the short summers
of high altitudes in the province often mean that four or five
years are spent in the larval stage. Adult dragonflies in British
Columbia live for about one to two months.
R.A. 2002. Introducing the dragonflies of British Columbia and
the Yukon. Royal British Columbia Museum, Victoria and University
of British Columbia Press, Vancouver.
R.A. and K.M. Stuart. 1977. The dragonflies of British Columbia.
British Columbia Provincial Museum Handbook No. 35. Victoria.
P.S. 1999. Dragonflies: behavior and ecology of Odonata. Cornell
University Press, Ithaca, N.Y. 829 pp.
J.G., M.J. Westfall, Jr., and M.L. May. 2000. Dragonflies of
North America. Scientific Publishers, Gainesville. 939 pp.
E.M. 1953. The Odonata of Canada and Alaska. Volume 1. Univ.
Toronto Press, Toronto. 292 pp.
E.M. 1958. The Odonata of Canada and Alaska. Volume 2. Univ.
Toronto Press, Toronto. 318 pp.
E.M. and P.S. Corbet. 1975. The Odonata of Canada and Alaska.
Volume 3. Univ. Toronto Press, Toronto. 307 pp.
M.J., Jr. and M.L. May. 1996. Damselflies of North America. Scientific
Publishers, Gainesville. 649 pp.
write up is extracted from the forthcoming publication by Scudder
and Cannings: the Insect Families of British Columbia.
Illustrations by L. L.
Lucas. Copyright © 2005 - All rights reserved