Coenagrion Kirby, 1890 and Enallagma Selys, 1875 (Coenagrionidae) - Bluets
Notes -Michigan SpeciesList - Key -References
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Page last updated: 11 March1999 (EB)
Notes on the Michigan Species of Coenagrion andEnallagma
Enallagma is awidespread genus of coenagrionids that is most speciose in NorthAmerica, with16 species now recorded in Michigan. Coenagrion is chiefly apalearctic genus in which three species occur in North America, with2 two species occuring here. Larvae are diagnostically a difficultgroup of damselflies. Only mature specimens with intact caudal gillscan be identified to species, and the works (Walker 1953; Westfall and May1996) upon which the key below is basedcaution about the reliability of keys. These moderate-sizeddamselflies closely resemble the larvae of Ischnura andCoenagrion, and diagnostic keys (Walker 1953, Westfall and May1996) upon which our key is baseddistinguish Coenagrion and Enallagma only at thespecies-level.
There is considerable debate regarding theviability of E. vernale Gloyd (1943), which Donnelly (1989) synomized with E.cyathigerum. Recent information andexamination of material as well as data from habitat separation (theformer inhabit lakes and rivers, the later principally bogs andheavily vegetated ponds) may indeed support the distinct identityargued for by Gloyd. Refer to Walker (1953) to distinguish between these two.
Most species inhabit lakes, ponds and wetlandsas well as slower portions of streams and rivers, usually withabundant aquatic vegetation. E.anna, E.aspersum, E. basidens,E. divagans, and E.traviatum are known only from the LP.Both E. anna and E.basidens appear to be expanding theirranges throughout North America, being found in sheltered coves andedges of large lakes, small ponds and slow portions of streams, aswell as human-impacted habitats such as impoundments and quarry ponds(Cannings1989, O'Brien andPratt, in press). E. antennatum,E. exsulans, E.geminatum, E. signatum andE. vesperum are known in the UP only from one record, but arewidespread in the LP. The other species (E. boreale,E. carunculatum, E. civile, the circumpolar E.cyathigerum, E. ebrium, andE. hageni)are widespread in both peninsulas. (See maps below).
Population cohorts for several species havebeen studied, though little generic-level concensus has been reached.Baker andClifford (1982) studied a population ofE. borealein a boreal forest pond in Alberta, Canada, and concluded that lowtemperatures during egg development strongly influenced subsequentgrowth of larvae, ultimately determining if there were one or twocohorts per year. Existence of mixed cohorts (bivoltine and uni- ormultivoltine) has also been observed for E. aspersum in NorthCarolina (Ingram and Jenner1976) and E. cyathigerum in Britain(Macan1964). The latter species also wasfound to be univoltine at another site in Britain (Johannsson1978), and Kormondy and Gower(1965) found E. ebrium to be univoltinein Pennsylvania as well. Pearlstone(1973) studied the feeding behavior ofE. borealein a small lake in southwestern British Columbia. Cladocerans andlarval chironomids were the principal prey items, although larvaeappeared opportunistic with prey choice as other prey items wereconsumed (e.g., mayflies, stoneflies, water mites, copepods, otherdamselflies, etc.). Prey choice also did not marked change among thevarious instars of mature instars.
Ecological information on the larvae ofCoenagrioncomes principally from Walker (1953), Baker and Clifford (1980) andCannings and Cannings (1980). Larvae are widely distributed innorthern latitudes, and is probably univoltine in Michigan.Walker(1953, p. 179) notes thatC. resolutum, which is widely distributed in Michigan (Map 1, below),inhabits a wide variety of lentic habitats, including "almost anysmall permanent or subpermanent body of still water...ordinary pondsand prairie sloughs with marshy borders; in springy cat-tail marshes;in dark calla ponds; in sphagnum pools, in cool northern spruce ortamarack swamps, and in the marginal vegetation of slow weedystreams." C.interrogatum, which is found only inthe northernmost part of Michigan, appears locally distributed inopen fens and marshes with abundant mosses (Cannings and Cannings1980).
Other links with information on the biology orecology of larval Coenagrion andEnallagma:back totop
Shetland,Scotland E. cyathigerum habitat information>>http://www.zetnet.co.uk/sigs/insects/dragon.html
Houston,Texas Enallagma with brief habitat notes>> http://www.io.com/~pdhulce/dragon3.html
IntroducedEnallagma civile to Hawaii >>http://www.bishop.hawaii.org/bishop/ento/Megalagrion/htmlPages/Mega01.shtml
Map 1: County distribution ofCoenagrionresolutum in Michigan
Click on map for a larger imageCoenagrioninterrogatum (Selys, 1876) - Subarctic Bluet
Coenagrion resolutum (Selys,1876) - Taiga Bluet - Map 1EnallagmaMap 1Map 2Map 3Map 4Map 5Map 6Map 7Map 8Map 9Map 10Map 11Map 12Map 13Map 14Map 15
Maps 1-15: County distribution for the Michigan species ofEnallagma
Click on map for a largerimageEnallagma anna Williamson - map under construction
Enallagma antennatum (Say,1839) - rainbow bluet - Map1
Enallagma aspersum (Hagen, 1861) - azure bluet - Map 2
Enallagma basidens Calvert, 1902 - double-striped bluet - Map 3
Enallagma boreale Selys,1875 - boreal bluet - Map4
Enallagma carunculatum Morse, 1895 - tule bluet - Map 5
Enallagma civile (Hagen, 1861) - familiar bluet - Map 6
Enallagma cyathigerum (Charpentier,1840) - northern bluet - Map7
Enallagma divagans Selys, 1876 - turquoise bluet - Map 8
Enallagma ebrium (Hagen, 1861) - marsh bluet - Map 9
Enallagma exsulans (Hagen, 1861) - stream bluet - Map 10
Enallagma geminatum Kellicott,1895 - skimming bluet - Map11
Enallagma hageni (Walsh, 1863) - Hagen's bluet - Map 12
Enallagma signatum (Hagen, 1861) - orange bluet - Map 13
Enallagma traviatum (syn.westfalli)Selys,1876 - slender bluet - Map14
Enallagma vesperum Calvert, 1919 - vesper bluet - Map 15back totop
Key toMature Larvae of Michigan Coenagrion and Enallagma
(Adapted from Walker1953 and Westfall and May1996)
Caution: only maturespecimens with intact lateral and medial gills can be reliabilyidentified to species unless an associated adult specimen isavailable.
1a. Second antennalsegment longer than first, third segment at least 2x longer thanfirst (Fig. 1); stout dorsal antenodal setae of median gill incomplete row, if present, although may be proximally minute (Fig. 2);gills with pigment usually restricted to the tracheae, sometimes with1-3 indistinct transverse stripes and/or an axial stripe (picture);eyes usually unpatterned (Fig. 4) - 2
Fig. 1 Fig. 2 Fig. 4
Fig. 1: Enallagmaebrium larva (25x,dorsal-lateral view), from Douglas Lake, Cheboygan Co., Michigan,collected by E. J. Kormondy on 19 June 1953. UMMZODO-2000. Fig. 2:same specimen as in Fig. 1 (25x, lateral view). Fig. 4: same specimenas in Fig. 1 (12x, dorsal view).
1b. Secondantennal segment not longer than first, third segment < 2x longerthan first (picture); stout dorsal antenodal setae of median gillwhole or partly reduced to slender hairs or confined to the vicinityof the nodus (picture); gills generally more extensively pigmented(picture); eyes usually patterned with dark stripes or spots(picture) - 14
2a.(1a). Gills with patches of closely branched and deeplypigmented tracheae, the intervening areas with mostly unpigmented andmuch less branched tracheae (picture) - 3
2b. Gills withthe tracheae uniformly and usually much less closely branched,pigmentation of the tracheae general although often interrupted byclear areas (picture) - 4
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3a.(2a). Cerci of male in dorsal view bluntly angular, theouter edge nearly straight and with an oblique ridge, in lateral viewbluntly rounded (picture); female apparently indistinguishable fromE. hageni- E. ebrium
3b. Cerci ofmale in dorsal view with an evenly curved margin and without a ridge,in lateral view bluntly angular (picture) - E. hageni
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4a.(2b). Dorsal antenodal setae of median gill fewer than20 (picture); cerci of male with deep dorsal concavity, easilyvisible in dorsolateral view, sometimes even with dorsal marginappearing concave in strict lateral view (picture), and in dorsalview subacute, slightly longer than wide (picture); median gillusually < 4.5 mm - E.geminatum
4b. Dorsalantenodal setae almost always 20 or more (picture); cerci of malewith concavity, if any, medial or slightly dorsomedial, not usuallyvisible in dorsolateral view (picture) and, if visible, cerci indorsal view appear more or less globular and wider than long(picture); median gill usually > 4.5 mm - 5
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5a.(4b). Dorsal and ventral series of stout antenodal setaeof median gill nearly equal in length and consisting of ratherclosely set setae (picture) - 6
5b. Dorsal andventral series of stout antenodal setae of median gill nearly 2x asventral series, with the latter consisting of comparatively small andwidely spaced setae (picture) - 7
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6a.(5a). Cerci in caudal view more rounded distally, in themale shaped like clenched boxing gloves seen end-on, the distalprojection more than 0.5 as wide (from dorsomedial to ventrolateralface) as long (picture); cerci in female with distal projectionusually higher than wide, set off from basal portion by a dorsal foldonly (picture) - E.boreale
6b. Cerci incaudal view less rounded distally, in the male with the distalprojection forming a distinct, transverse ridge that is less than 0.5as wide as long (measured from above); cerci in female with thedistal projection usually not higher than wide and set off from thebasal portion by dorsal and ventral folds (picture) -E. cyathigerum
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7a.(5b). Males, ovipositor rudiments absent (picture) -8
7b. Females,ovipositor rudiments present (picture) - 11
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8a.(7a). Cerci very large and robust, in dorsal view >0.38mm in length; dorsal antenodal series of setae of median gillusually extending at least 2/3 the length of the gill -E. anna
8b. Cercislenderer, in dorsal view < 0.35mm in length; antenodal setae ofgills variable - 9
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9a.(8b). Ventral surface of cerci strongly concave inventrolateral view (picture); bog-ponds - E. aspersum
9b. Ventralsurface of cerci broadly convex in ventrolateral view (picture) -10
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10a.(9b). Cerci in posterior view with maximum distance fromdorsomedial to ventrolateral margins greater than maximum distancefrom dorsolateral to ventromedial margins (picture); cerci usually< 0.3 mm long in dorsal view (picture) - E. carunculatum
10b. Cerci inposterior view with maximum dorsomedial to ventrolateral margins lessthan maximum dorsolateral to ventromedial distance (picture); cerciusually > 0.3 mm in dorsal view (picture) - E. civile
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11a.(7b). Length of cerci in dorsal view 0.29 mm or more -12
11b. Length ofcerci in dorsal view 0.28 mm or less - 13
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12a.(11a). Cerci with medial margin distinctly concave inventrolateral view - E.civile
12b. Cerciwith medial margin straight or barely concave in ventrolateral view -E. anna
13a.(11b). Cerci with medial margin slightly concave inventrolateral view (picture); axial tracheae of gills often appearingdistinctly coiled around each other basally (picture) -E. aspersum
13b. Cerciwith medial margin usually straight or convex, rarely very slightlyconcave, in ventrolateral view (picture) axial tracheae usually notappearing distinctly coiled around each other basally (picture) -E. carunculatum
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14a.(1b). Posterolateral margin of head rounded, at bestwith small lobes (picture); lateral carinae of abdomen projectingabruptly from the posterior part of each segment, but not prominentin front, the posterior margin bearing a group of stout setae butotherwise bare (picture); gills without patches of closely branchedand deeply pigmented tracheae (figure) - 15
14b. Posterolateral margin of head with prominent lobes(picture); lateral carinae of abdomen evident but not projectingabruptly from the posterior part of each segment, and (exceptE. basidens) bearing only slender hairs and, if any, few stoutsetae (figure); gills usually with patches of closely branched anddeeply pegment tracheae (figure) - 16
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15a.(12a). Dorsal margin of median gill without prominentstout setae (figure); median gill at most 3x as long as its greatestwidth, in lateral view distal 2/3 greatly expanded with dorsal marginstrongly convex (figure); tracheae of gills widely spaced, usuallydirectly opposite and perpendicular to the axis (figure) -E. vesperum
15b. Dorsalmargin of median gill with at least a few stout setae proximal to thenodus (figure), number of stout setae on ventral margin of lateralgills 45 or more, stout setae on lateral carina 30-40 (figure);median gill at least 3x as long as its greatest width, and wideninggradually from the base with the dorsal margin not so strongly convex(figure); tracheae more numerous than above, meeting axis at an acuteangle (figure) - E.signatum
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16a.(12b). Median gill (lateral gills often similar) with2-4 apical, dark, transverse bands often confluent with axis(figure); lateral carinae of abdomen projecting rather abruptly fromposterior part of each segment, with a scattered group of stout setaeon the prominence (figure); body length not including gills usually< 11 mm - E.basidens
16b. Mediangill without such dark apical bands, although an irregular anddiffuse dark area may be present (figure); lateral carinae of abdomenprominent but not projecting abruptly from the end of each segment,and generally bearing many slender hairs but few stout setae(figure); body length not including gills usually > 11 mm -17
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17a.(14b). Gills without a distinct nodus or abrupt colorchange beyond midlength, but with 4 or 5 widely spaced dark bandsformed by patches of closely brnached and darkly pigmented tracheae(figure); gills narrow, at least 6x long as wide (figure) -E. divagans
17b. Gillswith distinct abrupt color change (dark proximally, light distally)about 1/3 to 1/2 the distance from the apex (figure); gills wider,usually 4-6x long as wide (except E.antennatum) - 18
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18a.(15b). Median gill with stiff dorsal setae absent orindistinct (figure); gills usually dark brown from base to noduswhich is located 1/2 to 2/3 from base to apex (figure) -E. traviatum
18b. Mediangill usually with distinct stiff dorsal setae proximal to nodus(except E. antennatum) (figure); gills proximal to nodus usually lessdeeply pigmented or with pigment restricted to basal and axial areas(figure) - 19
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19a.(16b). Median gill without stiff, dorsal antenodalsetae, and without a definite nodus (figure); lateral gills verynarrow, 6-8x long as wide - E.antennatum
19b. Mediangill with 8-12 stiff, dorsal antenodal setae, and gill with adistinct nodus 1/2 the distance from base to apex (figure); lateralgills wider, 4-5x long as wide - E.exsulansback totop
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Baker, R. L.,and H. F. Clifford. 1982. Life cycle of an Enallagma boreale Selyspopulation from the boreal forest of Alberta, Canada (Zygoptera:Coenagrionidae). Odonatologica11(4):317-322.
Calvert, P. P. 1902,in Calvert, P. P. 1901-1908. Odonata. In Biologia CentraliAmericana: Insecta Neuroptera. R. H. Porter & Dulau & Co.:London. Dec 1902, p. 114.
Calvert, P. P. 1919.Gundlach's work on the Odonata of Cuba: a critical study.Transactions of the AmericanEntomological Society 45:335-396.
Cannings, R. A.1989. Enallagma basidens Calvert, a dragonfly new to Canada, with notes on theexpansion of its range in North America (Zygoptera: Coenagrionidae).Notulae Odonatologicae 3(4):53-55.
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 112:437-441.
Charpentier, T.de. 1840. Libellulinae europaeae descriptae e depictae. Lipsiae,Leopold Voss. 180 pp.
Donnelly, T. W.1989. The status of Enallagmacyathigerum (Charp.) andE. vernaleGloyd in south-central New York (Zygoptera: Coenagrionidae).Odonatologica 18:373-378.
Gloyd, L. K. 1943.Enallagma vernale, a new species of Odonata from Michigan.Occasional Papers of the Museum ofZoology, University of Michigan479:1-8.
Hagen, H. A. 1861.Synopsis of the neuroptera of North America, with a list of the SouthAmerican species. SmithsoniaMiscellaneous Collections 4:1-347.
Ingham, B. R.,and C. E. Jenner. 1976. Life histories of Enallagma hageni (Walsh)and E. aspersum (Hagen) (Zygoptera: Coenagrionidae). Odonatologica5:331-345.
Johannsson, O. E.1978. Co-existence of larval Zygoptera (Odonata) common to theNorfolk Broads (U.K.). Oecologia32:303-321.
Kellicot, D. S.1895. Catalogue of the Odonata of Ohio, Part 1. Journal of the Cincinnati Society of Natural History17:195-216.
Kirby, W. F. 1890. A synonymic catalog of NeuropteraOdonata or dragonflies. Guerney and Jackson, London. 202 pp.
Kormondy, E. J.,and J. L. Gower. 1965. Life history variations in an association ofOdonata. Ecology 46:882-886.
Macan, T. T. 1964. TheOdonata of a moorland fishpond. Int.Revue ges. Hydrobiol.49:325-360.
Morse, A. P. 1895. NewNorth American Odonata. Psyche 7:207-211.
O'Brien,M. F., and P. D. Pratt. 1999 (In press). Enallagma anna, adamselfly new to the Great Lakes region (Odonata: Coenagrionidae).The Great Lakes Entomologist32(1).
Pearlstone, P. S.M. 1973. The food of damselfly larvae in Marion Lake, BritishColumbia. Syesis 6:33-39.
Say, T. 1839.Descriptions of new North American neuropterous insects andobservations on some already described by (the late) Th. Say.Journal of the Academy of NaturalScience of Philadelphia 8:9-46.
Selys-Longchamps, E.de. 1875. Notes on Odonata from Newfoundland collected in 1874 by Mr.John Milne. Entomologists MonthlyMagazine 11:241-243.
Selys-Longchamps, E.de. 1876. Synopsis des agrionines, cinquième légion:Arion(suite). Le genre Agrion. Bulletin del'Académie royale des Sciences de Belgique (2) 42:480-531.
Walker, E. M. 1953.The Odonata of Canada and Alaska, Vol. 1. University of TorontoPress: Toronto, Ontario. xi + 292 pp.
Walsh, B. D. 1862.List of the Pseudoneuroptera of Illinois contained in the cabinet ofthe writer, with descriptions of over forty new species, and notes ontheir structural affinities. Proceedingsof the Entomological Society of Philadelphia 1862:361-402.
Walsh, B. D. 1863.Observations on certain N. A. neuroptera by Hagen, M. D., ofKonigsberg, Prussia; translated from the original French MS., andpublished by permission of the author, with notes and descriptions ofabout twenty new N. A. species of Pseudoneuroptera. Proceedings of the Entomological Society ofPhiladelphia 2:167-272. [note: see alsoWalsh, B. D.1862 for original description ofadults, which were named in Walsh 1863. Source: Westfall and May1996 ).
Westfall, M.J., Jr. and M. L. May. 1996. Damselflies of North America. ScientificPublishers: Gainesville, Florida. x + 650 pp.back totop