Zygoptera - Damselflies


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Page last updated: 01/26/2017

Notes on Michigan Nymphal Zygoptera

The 43 species of damselflies recorded in Michigan are divided into 3 families and 11 genera.

Slender and elongate, zygopteran nymphs are easily distinguished from anisopteran nymphs by the presence of caudal gills, and the thorax and abdomen being slender and not wider or narrower than the head. Nymphs are generally slow-moving clingers by habit, cryptic adherers to aquatic vegetation, debris or rocks. Some coenagrionids (Argia) are also found underneath large lotic substrates. The majority of our zygopteran taxa are lentic, inhabiting lakes, ponds, bogs, marshes, and backwater areas of streams and rivers. Prominent exceptions to this include nymphs of Calopterygidae (Calopteryx, Hetaerina), Lestidae (Archilestes grandis) and Coenagrionidae (Argia), which are lotic, and are found among the debris and vegetation alongside streambanks and occasionally underneath rocks. Samples of riffles and runs in lotic systems rarely produce nymphal specimens (except from drift).

Collected specimens should be handled gently. Particularly for lestid (Lestes) and some coenagrionid genera (Argia, Ischnura, Coenagrion, and Enallagma), antennal segments and caudal gills - very important species-level diagnostic characters - are quite fragile and easily fall off. These features can be damaged or lost when live specimens vigorously thrash about when handled with forceps. (nymphs can be anesthetized with soda water). I (EB) find the best means of storing nymphs are inside 70% alcohol-filled (ETOH) 0.25-dram vials placed inside alcohol-filled a 4-dram polyseal cap vial. (A drop or two of glyceryn in the larger vial further protects from dessication). This protects the specimen from excessive movements cause by movement or jarring of the vial that often result in fragile body parts breaking off, and also allowing one to keep track of those important parts (especially determining which is the lateral or median gill) that do break off. Often, immature nymphs cannot be identified to species, thus attemps should be made to collect mature nymphs, or rear specimens to the penultimate or adult stage, in order to assure accurate identification.

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Key to Michigan Families of Nymphal Zygoptera

1a. First antennal segment elongate, greater than segments 2-5 combined (Fig. 1); prementum with deep median cleft (Fig. 2) - Calopterygidae
Fig. 1 Calopteryx maculata Fig. 2 C. maculata

1b. First antennal segment not so elongate, less than segments 2-5 combined (Fig. 3); prementum with at most a tiny median cleft (Fig. 4) - 2

Fig. 3: Chromagrion conditum Fig. 4: C. conditum

2a.(1b). Basal half of labium greatly narrowed and elongate, folded labium extends back to mesocoxae or beyond (Fig. 5) - Lestidae
Fig 5: Lestes inaequalis

2b. Basal half of labium not greatly narrowed, folded labium extends back only to procoxae (Fig. 6) - Coenagrionidae
Fig. 6: C. conditum
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