COENAGRIONIDAE Kirby, 1890 - PondDamsels


Notes - Key -References
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Page last updated: 11 March1999 (EB)

Notes on Michigan Coenagrionidae

The most speciose group (30 species in 7genera) of Michigan damselflies, these are nearly ubiquitous denizensof nearly all aquatic habitats. Most species are found in lentichabitats, though several (principally Argia, someEnallagma)are found in lotic habitats or in backwater sections of streams andrivers with adequate aquatic vegetation. Life cycles are generallyunivoltine, though further north some may require an additional yearof development, and others (e.g., Ischnura, Enallagma) mayeven have multiple generations per year in the south.

Apparently antennal segment number, often usedto distinguish between Ischnura andCoenagrion(7) from Enallagma (6) ( Walker 1953, p. 173, Hilsenhoff1995), is unreliable (Baker and Clifford1980, Cannings and Cannings1980, Westfall and May1996). Michigan species are now beingexamined to elucidate clear differences. Until this study can becompleted, however, we provide a key that will separateIschnurafrom Coenagrion and Enallagma.


Generic Key to Mature Larvae of MichiganCoenagrionidae
(Adapted from
Walker1953, Westfall and May1996, and Westfall andTennessen 1996)

1a. Dorsal premental setaeabsent (picture); distal margin of lateral lobe produced into 2distal pointed hooks (picture); in dorsal view, caudal gills usuallyquite thick or triquetral (picture); principally lotic -Argia

1b. Dorsalpremental setae present (picture); distal margin of lateral lobe with1 distal pointed hook, and a truncate, denticulate lobe (picture);caudal gills in dorsal view never triquetral or thick (picture);usually lentic - 2


2a.(1b). Posterolateral margins of head sharply angulate(picture) - 3

2b.Posterolateral margins of head broadly rounded (picture) -4
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3a.(2a). Antennae 6-segmented (picture); caudal gills about1/3 as broad as long, margins with sparsely situated setae (picture)- Amphiagrionsaucium

3b. Antennae7-segmented (picture); caudal gills about 1/6 as broad as long,margins thickly beset with setae (picture) - Chromagrionconditum
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4a.(2b). Mentum with 1 or 2 dorsal setae on each side ofmedian line, the second, when present, very small (picture); palpalsetae generally 6 - Nehalennia

4b. Mentumwith 3 to 7 dorsal setae of normal length on each side of median line(picture) - 5
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5a.(4b). Antennae usually with 7 clearly distinguishedsegments (picture); eyes usually with distinct banding pattern(picture); lateral carinae of Ab2-7 with small setae usually notarranged in a single row (picture) - Ischnura

5b. Antennaeusually only with 6 clearly distinguished segments, last (apical)segment sometimes with a diffuse, unclear suture that may be ringedwith thin setae making it appear separated (picture); eyes not withbanding pattern as above, with or without dark stripes or ahexagonial pattern (picture) - Coenagrion,Enallagma
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References

Baker, R. L.,and H. F. Clifford. 1980. The nymphs of Coenagrion interrogatumand C. resolutum (Zygoptera: Coenagrionidae) from the boreal forest ofAlberta, Canada. The CanadianEntomologist 112(5):433-436.

Cannings,S. G., and R. A. Cannings. 1980. The larva of Coenagrion interrogatum(Odonata: Coenagrionidae), with notes on the species in the Yukon.The CanadianEntomologist 112(5):437-441.

Hilsenhoff, W. L.1995. Aquatic insects of Wisconsin. Keys to Wisconsin genera andnotes on biology, distribution and species (3rd Ed.). PublicationNumber 3 of the Natural History Museums Council, University ofWisconsin-Madison (1995).

Kirby, W. F. 1890. Asynonymic catalog of Neuroptera Odonata or dragonflies. Guerney andJackson, London. 202 pp.

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

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

Westfall,M. J., and K. J. Tennessen. 1996. Odonata, pp. 164-211.In AnIntroduction to the Aquatic Insects of North America, 3rd Ed.Merritt, R. W. and K. W. Cummins (eds.). Kendell/ Hunt PublishingCompany: Dubuque, Iowa.

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