COENAGRIONIDAE Kirby, 1890 - Pond Damsels


Notes - Key - References
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Page last updated: 11 March 1999 (EB)

Notes on Michigan Coenagrionidae

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

Apparently antennal segment number, often used to distinguish between Ischnura and Coenagrion (7) from Enallagma (6) ( Walker 1953, p. 173, Hilsenhoff 1995), is unreliable (Baker and Clifford 1980, Cannings and Cannings 1980, Westfall and May 1996). Michigan species are now being examined to elucidate clear differences. Until this study can be completed, however, we provide a key that will separate Ischnura from Coenagrion and Enallagma.


Generic Key to Mature Larvae of Michigan Coenagrionidae
(Adapted from
Walker 1953, Westfall and May 1996, and Westfall and Tennessen 1996)

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

1b. Dorsal premental setae present (picture); distal margin of lateral lobe with 1 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 about 1/3 as broad as long, margins with sparsely situated setae (picture) - Amphiagrion saucium

3b. Antennae 7-segmented (picture); caudal gills about 1/6 as broad as long, margins thickly beset with setae (picture) - Chromagrion conditum
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4a.(2b). Mentum with 1 or 2 dorsal setae on each side of median line, the second, when present, very small (picture); palpal setae generally 6 - Nehalennia

4b. Mentum with 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 distinguished segments (picture); eyes usually with distinct banding pattern (picture); lateral carinae of Ab2-7 with small setae usually not arranged in a single row (picture) - Ischnura

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

Baker, R. L., and H. F. Clifford. 1980. The nymphs of Coenagrion interrogatum and C. resolutum (Zygoptera: Coenagrionidae) from the boreal forest of Alberta, Canada. The Canadian Entomologist 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 Canadian Entomologist 112(5):437-441.

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

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

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.

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

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