Coenagrion Kirby, 1890 - Bluets

Notes - Michigan Species List - Key - References
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Page last updated: 01/12/2017

Notes on the Michigan Species of Coenagrion

Chiefly a Palaearctic genus, three species are known from North America, of which two reach our area. These moderate-sized damselflies closely resemble the larvae of Enallagma and Ischnura, and diagnostic keys (Walker 1953, Westfall and May 1996) often include these species with Enallagma. Westfall and May (1996) also believe that a commonly used diagnostic - 6 vs. 7 antennal segments - is not reliable.

Larvae are widely distributed in northern latitudes, and is probably univoltine in Michigan.
Walker (1953, p. 179) notes that C. resolutum, which is widely distributed in Michigan (Map 1, below), inhabits a wide variety of lentic habitats, including "almost any small permanent or subpermanent body of still water...ordinary ponds and prairie sloughs with marshy borders; in springy cat-tail marshes; in dark calla ponds; in sphagnum pools, in cool northern spruce or tamarack swamps, and in the marginal vegetation of slow weedy streams."


Map 1: County distribution of Coenagrion resolutum in Michigan
Click on map for a larger image

C. interrogatum is found on Isle Royale, as well as the counties of Houghton, Iron, Keweenaw, Gogebic, Marquette, Mackinac, and Schoolcraft, and inhabits cold swamps and open bogs, partial to areas of open bog or marsh (Walker 1953, p. 181-183).

Links on the biology or ecology of larval Coenagrion:
no links found as of 15 January 1998

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Michigan Species List

Coenagrion interrogatum (Selys, 1876) - Subarctic Bluet
Coenagrion resolutum (Selys, 1876) - Taiga Bluet

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Key to Mature Larvae of Michigan Coenagrion
(Adapted from
Westfall and May 1996)
Click on species' name for Michigan range map

1a. Median gill < 5x as long as wide, and usually slightly acuminate apically (picture); cerci of male without a dorsomedial concavity (picture); ovipositor rudiments of female extending more than 0.6 mm beyond posterior row of denticles on sternum of abdominal segment 9 (picture); metafemur usually > 2.9 mm - C. resolutum

1b. Median gill ca. 5x as long as wide, and usually not acuminate apically (picture); cerci of male with distinct dorsomedial concavity (picture); ovipositor rudiments of female extending < 6.0 mm beyond posterior row of denticles on sternum of segment 9 (picture); metafemur usually < 2.9 mm - C. interrogatum

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References

Kirby, W. F. 1890. A synonymic catalog of Neuroptera Odonata or dragonflies. Guerney and Jackson, London. 202 pp.

Say, T. 1839. Descriptions of new North American neuropterous insects and observations on some already described by (the late) Th. Say. Journal of the Academy of Natural Science of Philadelphia 8:9-46.

Selys-Longchamps, E. de. 1876. Synopsis des agrionines, cinquième légion: Arion (suite). Le genre Agrion. Bulletin de l'Académie royale des Sciences de Belgique (2) 42:480-531.

Walker, E. M. 1953. The Odonata of Canada and Alaska, Vol. 1. University of Toronto Press: Toronto, Ontario. xi + 292 pp.

Westfall, M. J., Jr. and M. L. May. 1996. Damselflies of North America. Scientific Publishers: Gainesville, Florida. x + 650 pp.

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