Zygoptera - Damselflies

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Page last updated: 18February 1998

Notes on Michigan Larval Zygoptera

The 43 species of damselflies recorded inMichigan are divided into 3 families and 10 genera.

Slender and elongate, zygopteran larvae areeasily distinguished from anisopteran larvae by the presence ofcaudal gills, and the thorax and abdomen being slender and not wideror narrower than the head. Larvae are generally slow-moving clingersby habit, cryptic adherers to aquatic vegetation, debris or rocks.Some coenagrionids (Argia) are also foundunderneath large lotic substrates. The majority of our zygopterantaxa are lentic, inhabiting lakes, ponds, bogs, marshes, andbackwater areas of streams and rivers. Prominent exceptions to thisinclude larvae of Calopterygidae (Calopteryx, Hetaerina),Lestidae (Archilestesgrandis) and Coenagrionidae(Argia),which are lotic, and are found among the debris and vegetationalongside streambanks and occasionally underneath rocks. Samples ofriffles and runs in lotic systems rarely produce larval specimens(except from drift).

Collected specimens should be handled gently.Particularly for lestid (Lestes) and somecoenagrionid genera (Argia, Ischnura,Coenagrion, and Enallagma), antennalsegments and caudal gills - very important species-level diagnosticcharacters - are quite fragile and easily fall off. These featurescan be damaged or lost when live specimens vigorously thrash aboutwhen handled with forceps. (Larvae can be anesthetized with sodawater). I (EB) find the best means of storing larvae are inside 70%alcohol-filled (ETOH) 0.25-dram vials placed inside alcohol-filled a4-dram polyseal cap vial. (A drop or two of glyceryn in the largervial further protects from dessication). This protects the specimenfrom excessive movements cause by movement or jarring of the vialthat often result in fragile body parts breaking off, and alsoallowing one to keep track of those important parts (especiallydetermining which is the lateral or median gill) that do break off.Often, immature larvae cannot be identified to species, thus attempsshould be made to collect mature larvae, or rear specimens to thepenultimate or adult stage, in order to assure accurateidentification.

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Key to Michigan Families of LarvalZygoptera

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

1b. Firstantennal 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:Chromagrionconditum Fig.4: C. conditum

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

2b. Basal halfof labium not greatly narrowed, folded labium extends back only toprocoxae (Fig. 6) - Coenagrionidae
Fig.6: C.conditum
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