Notes - Michigan Species List - Key - References
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Page last updated: 17 July 1998
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."
C. interrogatum, currently known only from one record on Isle Royal, 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
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
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.