Aeshna Fabricius,1775 -Darners


Notes -Michigan SpeciesList - Key -References
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Page last updated: 10August 1998

Notes onthe Michigan Species of Aeshna

Aeshna is themost speciose holarctic genus of Aeshnidae, and twelve species occurin Michigan (see maps below). As adults are strong fliers, most ofour species - A.canadensis, A. clepsydra,A. constricta, A.interrupta, A. tuberculifera,A. umbrosaand A. verticalis - are widely distributed and recorded from both the LPand UP. Four species are northernly in distribution: A. eremita andA. sitchensis have been recorded only in the UP and the northern LP,A. subarctica only in the UP, and A.juncea, a holarctic species, recordedonly from Isle Royale in Lake Superior. A. mutata has been foundonly in the southern part of the LP.

Larvae usually are found clinging to vegetationin lakes and ponds as well as slower sections of streams and rivers.As their clinging habits often make them conspicuous, largerspecimens are often subject to fish predation. However, the tablesmay be turned, with larval and small juvenile fish being included inthe diet of larger Aeshna individualstogether with other aquatic invertebrate organisms.

With some rather subjective determinations ofdiagnostic features, some earlier keys for aeshnid larvae(e.g., Needham and Westfall1955) are not reliable for manyspecies. Fortunately, Walker's (1958) outstanding treatment of the Canadian species workswell for Michigan, and the key below is modified from the wealth ofinformation provided in that work as well as from measurements oflarval specimens here at UMMZ. Species-level determinations oftenrequires a microscope with an eyepiece equipped with measuringgraticule to permit accurate measurement of labium width-to-lengthratios as well as the length of female larvae' developing genitalstructures.

Other links with information on the biology orecology of larval Aeshna:
Ottawa,Ontario survey, with brief habitat notes >> http://www.cyberus.ca/~jdsankey/odon2.html
Abstractfrom faunal survey in Szigetköz,Hungary >>http://origo.hnm.hu/danube_dg/e5ambrus.html
Briefhabitat notes from New Jersey, USA>> http://www.hsrl.rutgers.edu/cumb.cape.html
Studyexamining effects of contaminant-bound sediments on Aeshna larvae's predationefficiency >>http://www.ecotox.lu.se/ECOTOX/th_met.html

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MichiganSpecies List

Map 1Map 2Map 3
Map 4Map 5Map 6
Map 7Map 8Map 9
Map 10Map 11Map 12
Maps 1-12: County distribution of the Michigan species of
Aeshna
Click on map for largerimage

AeshnacanadensisWalker,1908 - Canada darner - Map1
Aeshna clepsydra
Say, 1839 - Mottled Darner - Map 2
Aeshna constricta
Say, 1839 - Lance-tipped Darner - Map 3
Aeshna eremita
Scudder, 1866 - Lake Darner - Map 4
Aeshna interrupta
Walker, 1908 - Variable Darner - Map 5
Aeshna juncea
(Linnaeus, 1758) - Rush Darner - Map 6
Aeshna mutata
Hagen, 1861 - Spatterdock Darner - Map 7
Aeshna sitchensis Hagen,1861 - Zigzag Darner - Map8
Aeshna subarctica
Walker, 1908 - Subarctic Darner - Map 9
Aeshna tuberculifera
Walker, 1908 - Black-tipped Darner - Map 10
Aeshna umbrosa
Walker, 1908 - Shadow Darner - Map 11
Aeshna verticalis
Hagen, 1861 - Green-striped Darner - Map 12

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Key to Mature Larvae ofMichigan Aeshna
(Reference: Walker 1958)

1a. Palpal lobes taperingto slender, slightly curved points (picture); female genitalia ofmature larvae very long, > 1.45x the mid-dorsal ventral length ofAb9 - A. constricta

1b. Palpallobes abruptly hooked, or truncate (picture); female genitaliashorter than above, < 1.40x the mid-dorsal vental length of Ab9 -2


2a.(1b). Antennae 6-segmented; no lateral spine on Ab6 ;female genitalia of mature larvae about 1.3x the mid-dorsal ventrallength of Ab9; muskeg bogs and sphagnum pools - A. sitchensis

2b. Antennae7-segmented; lateral spine on abdominal segment 6; female genitalia< 1.25x the mid-dorsal ventral length of Ab9 - 3
Back to previouscouplet (1)


3a.(2b). Lateral spine on Ab5 (may be minute) (picture);posterolateral margin of head somewhat obtuse-angulate (picture) -A. eremita

3b. No lateralspine on Ab5 (picture); posterolateral margin of head rounded(picture) - 4
Back to previous couplet(2); Back to beginning ofkey


4a.(3b). Folded labium elongate and very long, its distalwidth about 0.55x its length, and posteriorly reaching level withhind coxa (picture); female genitalia of mature larvae about 1.2x themid-dorsal ventral length of Ab9 (picture); usually resident of bogponds - A.tuberculifera

4b. Foldedlabium stouter, its distal width > 0.60x its length (picture), andreaching no farther than the middle coxa; female genitalia < 1.13xthe mid-dorsal ventral of Ab9 -5
Back to previouscouplet (3); Back to beginning ofkey


5a(4b). Labium long and narrow, width in folded position< 0.63x its length (picture); femur and tibiae dark withdistinct pale light (usually 3) bands (picture); eyes widest in frontof middle (using posterolateral margin of eye as posterior limit ofmeasurement) (picture); postocular margin of head straight (picture);streams, forest lakes and partly shaded pools and ponds -A. umbrosa

5b. Labiumwider, > 0.63x it length (picture); femur striped or uniform, buttibae not with 3 bands and often unifrom (picture); eyes widest ator slightly behind middle (picture); postocular margin of headslightly convex (picture) - 6
Back to previous couplet(4); Back to beginning ofkey


6a.(5b). Width of folded labium 0.78-0.80x of its length;southern LP, woodland swamps and bog-margined pools -A. mutata

6b. Width offolded labium < 0.75x of its length, usually < 0.70x (picture)- 7
Back to previouscouplet (5); Back to beginning ofkey


7a.(6b). Femora dark with three pale annuli (can fade witholder specimens), tibiae may also have pale banding (picture);abdomen marked with irregular pale blotches on a darker ground color(picture); dark submarginal blotch behind eye(picture) - A. interrupta

7b. Femorauniform (picture); abdomen more or less distinctly marked with darkmedian longitudinal stripe bordered by pale stripes (picture);submarginal blotch behind eye, if present, paler (picture) -8
Back to previous couplet(6); Back to beginning ofkey


8a.(7b). Lateral spine on Ab6 vestigial (picture);longitudinal stripes of abdomen somewhat broken into segmental spots,not always distinct, the dark median strip no darker than the lateraldark areas (picture) - 9

8b. Lateralspine on Ab6 small but not vestigial (picture); longitudinal stripesof abdomen clear-cut, the median stripe usually darker than thelateral dark areas (picture) - 10
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9a.(8a). Palpal lobes > 1.50x as wide as the movablehook at its basal articulation, the distal margin squarely truncateand the outer distal angle little rounded (picture); cerci of maleabout 0.33x longer than male projection of epiproct, their apicesvery slightly incurved (picture); general surface dull (picture) -A.juncea

9b. Palpallobes < 1.50x as wide as the movable hook at its basalarticulation, the outer distal angle broadly rounded (picture); cerciof male about 0.50x longer than the male projection, their apicesdecidedly incurved (picture); general surface polished (picture) -A. subarctica
Back to previous couplet(8); Back to beginning ofkey


10a.(8b). Palpal lobes squarely truncate with outer distalangle very little rounded, the opposing distal margins of the pairedlobes parallel (picture) - A.verticalis

10b. Palpallobes not squarely truncate, the outer distal distinctly rounded, theopposing distal margins of the paired lobes not parallel (picture) -11
Back to previous couplet(8); Back to beginning ofkey


11a.(10b). Palpal lobes each terminating in a very abruptlycurved and almost truncate hook (picture) dark median stripe deepenedabout the dorsal punctata (picture) - A. canadensis

11b. Palpallobes each terminating in a broadly curved hook (picture); darkmedian stripe of abdomen not deepened about the dorsal punctata(picture) - A. clepsydra
Back to previouscouplet (10); Back to beginning of key

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References

Fabricius, J. C.1775. Systema entomologiae. Libraria Kortii: Flensburg & Leipzig.424 pp.

Hagen, H. A. 1861.Synopsis of the Neuroptera of North America, with a list of the SouthAmerican species. SmithsonianMiscellaneous Collections4:1-347.

Linne, C. 1758.Systema naturae. Editio decima reformata. Holmiae. 543 pp.

Needham, J.G. and M. J. Westfall, Jr. 1955. A Manual of the Dragonflies of NorthAmerica (Anisoptera). University of California Press: Berkeley,California. xii + 615 pp.

Say, T. 1839. Descriptions of new North Americanneuropterous insects and observations on some already described by(the late) Th. Say. Journal of theAcademy of Natural Science of Philadelphia 8:9-46.

Scudder, S. H. 1866.Notes on some Odonata from the White Mountains of New Hampshire.Proceedings of the Boston Society ofNatural History 10:211-222.

Walker, E. M. 1908. Akey to the North American species of Aeshna found north ofMexico. The Canadian Entomologist40(11):377-391, (12):450-451, pl.10.

Walker, E. M. 1958.The Odonata of Canada and Alaska, Vol. 2. University of TorontoPress: Toronto. xii + 318.

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