Saskatchewan Dragonflies and Damselflies (Odonata)

agrion adult

To the general public dragonflies (suborder Anisoptera) and damselflies (suborder Zygoptera) are some of the most conspicuous aquatic insects we have in the province. The adults are large enough and colourful enough that, as in birding, many can be identified relatively easily in the field. In North America there are 11 families and about 650 species of Odonata. In Saskatchewan at least 28 species of Zygoptera and 52 species of Anisoptera have been recorded. One of our most spectacular damselflies is Calopteryx aequabilis (Calopterygidae), which have a beautiful metallic green abdomen and black wing tips (see above).

The adults of both suborders have four wings and an elongated abdomen. The dragonflies and Lestidae hold their wings spread out at rest while at rest. The Calyopterygidae and Coenagrionidae hold their wings over the abdomen. The Lestidae usually have a yellow, bronze or metallic green sheen to them. The Coenagrionidae are usually blue with black markings.

The life cycle consists of an egg and a multi-instar larval stage that transforms into the adult. In Saskatchewan a life cycle takes at least one year to complete and in some habitats two years or more may be required. Larvae inhabit all types of standing and running water. Most cling to submerged vegetation or crawl through the debris. Two general larval forms exist; dragonfly larvae are robust while the larvae of damselflies are elongated with with flat "gills" at the caudal end. When it is time to emerge into the adult a larva crawls out of the water onto a piece of vegetation, a rock or the shoreline. Once the adult emerges the larval exuvium (cast skin) is left behind.

Both the adult and larval stages are predatory. The larvae feed on all types of aquatic invertebrates. Larger dragonfly larvae will even attack tadpoles and small fish. Prey is either stalked amongst the vegetation or ambushed. When a prey item is within range the larvae rapidly extends a hinged mouthpart with toothed jaws that grasp the prey and pulls it to the mouth where it is devoured by strong chewing mandibles. As adults they capture flying insects in a basket created by the spiny legs. The adults also search out and pick off insects that are resting on vegetation.

There seems to be an urban/rural myth that "dragonflies" consume vast quantities of mosquitoes. I have heard news casts purporting they "eat 30% of their body weight in mosquitoes a day". Unfortunately, most larval dragonflies and damselflies are unable to live in the typical ephemeral pools and ponds that are the most prolific breeding habitats for mosquitoes. Similarly, as adults, dragonflies feed on a variety of flying insects including midges (non-biting midges (Chironomidae) and phantom midges (Chaoboridae), mothes and even each other. The proportion of mosquitoes in a dragonfly's diet is likely not that great. What seems to occur is people notice a decrease in mosquitoes in late July and August which regularly coincides with the appearance of large numbers of dragonflies. What is likely occurring is that most of the large populations of "spring" mosquito species have run through their life cycles, have laid eggs and are no longer flying. Other, multivoltine species, are not finding appropriate habitats to breed as the temporary pools, numerous in the spring, have dried out except in areas of exceptional thunderstorms.

The adults are relatively long lived and exhibit a number of interesting behaviours. Evidence suggests adults of Anax junius migrate from the northern states into the southern part of Canada, including Saskatchewan, in early spring. They mate and lay their eggs. The new generation emerges in autumn and migrates south.

Males of many species are extremely territorial. They set up a territory where there are good oviposition sites and vigorously defend it from other males and challenge other dragonfly species and other animals that enter their territory.

The mating procedure of odonates is unique. The male sperm transfer organs are located on the second abdominal segment. Before mating they curl the end of the abdomen up to the second segment to transfer the sperm. The end of the male abdomen has claspers that grasp the female by the prothorax or head. The female then curls her abdomen upwards to reach the transfer organs. Once mating is complete the pair will often fly in tandem. This enables the male to protect the female from other males while she is ovipositing.

Below is a basic larval key to the families of dragonflies and damselflies found in Saskatchewan.

1a: End of abdomen has three leaf-like structures (gills). One or all of these may be broken off. Body elongated.--Zygoptera (Damselflies)--Go to 2

1b: End of abdomen not as above, with a short "cone" structure made up of a number of parts. Body overall much fatter and robust in appearance than above.--Ansioptera (Dragonflies)--Go to 4

2a: First antennal segment much longer and thicker than all the rest combined.--Calopterygidae

2b: First antennal segment similar to the remaining segments in size.--3

3a: The pincer part of the mouth parts on a long stalk that usually extends well beyond bases of forelegs when folded at rest.--Lestidae

3b: The pincer on a shorter stalk. When folded it barely extends beyond forelegs.--Coenagrionidae

4a: Mouth parts when folded at rest cover the front of the head like a mask up to just below the eyes.--Libellulidae OR Corduliidae (These two families are considered by some authors as being subfamilies together with Macromiinae (not in SK), in the family Libellulidae.)

4b: Mouth parts are flat and held under the head when folded at rest.--5

5a: Antennae with six or seven segments all similar shape size.--Aeshnidae

5b: Only 4 antennal segments. The third segment is much longer and thicker than the others.--Gomphidae

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References:

Beukeboom, L.W. and M. Wasscha. 1986. Odonata collected in Canada in 1983. Notulae Odontologicae. 2:129-131.

Catling, P.M. and B. Kostiuk. 2004. Three additions to the Odonata of Saskatchewan, and some notable records. Argia 16:18-20.

Catling, P.M. and B. Kostiuk. 2004. Dragonflies recorded in 2004 from the Saskatchewan portion of the Cypress Hills Interprovincial Park. Argia 16:20-21.

Clifford, H.F. 1991. Aquatic Invertebrates of Alberta. University of Alberta Press.

Dunkle, S.W. 2000. Dragonflies through Binoculars: A field guide to the dragonflies of North America. Oxford Press.

Halstead, D. 2013. Prince Albert hosts the DSA Annual Meeting 2013. Newsletter Entomological Society of Saskatchewan. Vol. 32. pp 4-6.

Hilton, D.F.J. 1985, Dragonflies (Odonata) of Cypress Hills Provincial Park, Alberta and their biogeographic significance. Can. Ent. 117:1127-1136.

Hutchings, G. and D. Halstead. 2011. Dragonflies and Damselflies in the hand: An identification guide to boreal forest odonates in Saskatchewan and adjacent Regions. Special Publication #29. Nature Saskatchewan, Regina.

Hutchings, G.E. 2005. A list of the Odonata of Athabasca Sand Dunes Provincial Wilderness Park, SK. Blue Jay 63:87-93.

Hutchings, G.E. 2004. Eight new species or previously unrecorded species of Odonata (dragonflies) for Saskatchewan. Blue Jay, 62:98-103.

Needham, J.G., M.J. Westfall Jr. and M.L. May. 2000. Dragonflies of North America. Scientific Publishers, Gainesville, FL.

Tennessen, K.J. 2008. Chapter 12: Odonata. In. Merritt R.W., K.W. Cummins and M.B. Berg. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

Walker, E.M. 1953. The Odonata of Canada and Alaska. Vol. One. Part I: General. Part II: The Zygoptera-Damselflies. University of Toronto Press, Toronto.

Walker, E.M. 1958. The Odonata of Canada and Alaska. Vol. Two. Part III: The Anisoptera- Four Families. University of Toronto Press, Toronto.

Walker, E.M. and P.S. Corbet. 1975.The Odonata of Canada and Alaska. Vol. Three. Part III: The Anisoptera- Three Families. University of Toronto Press, Toronto.

Westfall, M.J. Jr. and M. L. May. 1996. Damselflies of North America. Scientific Publishers, Washington.