Canada darner
Male (top) and female (bottom)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Odonata
Infraorder: Anisoptera
Family: Aeshnidae
Genus: Aeshna
Species:
A. canadensis
Binomial name
Aeshna canadensis
Walker, 1908
Range of Aeshna canadensis

Aeshna canadensis, the Canada darner, is a species of dragonfly in the family Aeshnidae. It is common throughout southern Canada and the northern United States.[2][3]

Description

Adult Canada darners, similar to other members of the genus Aeshna, are relatively large, slender dragonflies, and are predominantly dark brown with paler blue or green markings.[4][5] Adults are 64 to 73 mm in total length.[5] The thorax has two vertical stripes on each side, the front with a prominent notch and an extension at the top.[5] The abdomen has spots on most segments.[5] The pale markings are usually blue in males and range from yellow-green to blue in females. The eyes are bluish in males and yellowish or bluish in females.[5] The pale markings may turn gray at colder temperatures.[5]

The green-striped darner is very similar, but is distinguished by minor differences in the shape of the markings and in typically having green thorax stripes.[5] The lake darner is also similar but is larger and has a distinct dark stripe across the face.[5]

Taxonomy

The Canada darner was first scientifically described in 1908 by Canadian entomologist Edmund Murton Walker, in the same publication as the first descriptions of black-tipped darner, shadow darner, subarctic darner, and variable darner, .[6]

Distribution

Canada darners are found from Newfoundland and New Jersey in the east to Yukon in the west.[5] Populations extend further south down the Appalachian mountains to West Virginia and south in mountain ranges to California and Montana.[5][7] There is an isolated population in Nebraska.[5]

Life history

nymph
illustration of emergence from larval exuvia

Canada darners spend most of their lives as an aquatic nymph.[7] Larvae are typically found in lakes and ponds, especially bog ponds and beaver ponds.[5] Breeding ponds typically have abundant emergent vegetation.[5] An Ontario study found that the species was restricted to ponds with a pH of no more than 6.2.[8] One study found that larvae may spend either one or two winters underwater before emerging.[7]

Adult males fly slowly along the shores of breeding ponds, sometimes dropping to the surface to search for females.[5] Mating occurs in shrubs nearby.[5] Females lay eggs at water level, usually in marshy vegetation away from shore.[5] Breeding adults are most active in sunny weather.[4]

female laying eggs

Away from breeding sites, adult Canada darners are often found with other darner species in feeding swarms in clearings and along roadways in early evening.[4][5] Adult Canada darners may be seen from June to October.[5]

Canada darners are often considered to be a common to abundant species where they are found.[4][8][9][7] Although the species has not generally been recognised as migratory, a study in Manitoba and Minnesota found that at least some populations of Canada darners undertake north-south migratory movements within their range.[7]

References

  1. ↑ Paulson, D.R. (2017). "Aeshna canadensis". IUCN Red List of Threatened Species. 2017: e.T165074A65830832. doi:10.2305/IUCN.UK.2017-3.RLTS.T165074A65830832.en. Retrieved 13 November 2021.
  2. ↑ Dunkle, S.W. (2000). Dragonflies through Binoculars: A Field Guide to Dragonflies of North America. New York: Oxford University Press, p.55.
  3. ↑ Mead, Kurt. (2017). Dragonflies of the North Woods. 3rd edition. Duluth, MN: Kollath+Stensaas, p.34-35.
  4. 1 2 3 4 Boole, Marilee S.; Hamrum, Charles L.; Anderson, Myron A. (1974). "The Minnesota Species of Aeshna with Notes on their Habits and Distribution (Odonata: Aeshnidae)". The Great Lakes Entomologist. 7 (1): 19–22.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Paulson, Dennis (2011). Dragonflies and Damselflies of the East. Princeton, New Jersey: Princeton University Press. ISBN 9780691122823.
  6. ↑ Walker, E. M. (1908). "A Key to the North American Species of Aeshna Found North of Mexico". The Canadian Entomologist. XL (11): 377–391.
  7. 1 2 3 4 5 Schilling, Emily Gaenzle; Kardynal, Kevin J.; Kundel, Holly; Crews-Erjaveck, Zephyr; Zobitz, John M.; Hobson, Keith A. (2020). "Phenological and Isotopic Evidence for Migration as life History Strategy in Aeshna canadensis (Family: Aeshnidae) Dragonflies". Ecological Entomology. doi:10.1111/een.12953.
  8. 1 2 Pollard, Bruce J.; Berill, Michael (1992). "The Distribution of Dragonfly Nymphs across a pH Gradient in South-central Ontario Lakes". Canadian Journal of Zoology. 70: 878–885.
  9. ↑ Rith-Najarian, J. C. (1998). "The Influence of Forest Vegetation Variables on the Distribution and Diversity of Dragonflies in a Northern Minnesota Landscape: A Preliminary Study (Anisoptera)". Odonatologica. 27 (3): 336–351.
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