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Notes on the Anisoptera

The 113 species of dragonflies so far recordedin Michigan are divided into 7 families and 36 genera. The larvae ofAnisoptera are distinguished from that of Zygoptera by a more robustshape, such that the thorax and abdomen are generally wider than thehead, and that respiration chiefly occurs by expansion andcontraction of abdominal muscles that move water in and out of therectal chamber across gills located within this structure. This alsopermits larvae to achieve rapid bursts of speed in the water. Larvaeof Michigan Anisoptera inhabit just about every type of aquaticecosystem in the state, from the largest of lakes to the smallest bogpool, from the very small woodland seeps to the largest of ourrivers. Our species of Cordulegaster generally are found only inseeps and streams, and the only species of Petaluridae found inMichigan - Tachopteryx thoreyi- probably is found only in leafymaterial in the upper portions of forested seeps, and is probably ouronly odonate that can breathe air (semiterrestrial).

The similarity in morphology among the larvae of Libellulidae,Corduliidae and Macromiidae has led some to group these assubfamilies in Libellulidae. As of yet, no one morphologicalcharacter has been found to reliably separate larvae of Corduliidaefrom Libellulidae, although characters suggested by
Walker and Corbet(1975) and Westfall andTennessen (1996) - cerci at least 0.5xthe length of the paraprocts (Corduliidae), less than 0.5x length(Libellulidae); distal edge of labial palp rather deeply dentate(Corduliidae), shallowly dentate or almost entire (Libellulidae) -works well for most of Michigan's larval species. The status ofMacromiidae as a family is not yet clear, and many authorities retainit as a subfamily of Corduliidae (e.g., Westfall andTennessen 1996). Certain larval (and adult) characters, however,separate these larvae from both Corduliidae and Libellulidae (seeGloyd1959). Hopefully a thoroughmorphological, molecular and ecological study of the entire groupwill one day resolve the matter.

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Key to the Michigan Familiesof Anisoptera Larvae
(References: Walker and Corbet1975, Westfall andTennessen 1996 and Wright and Peterson1944)

1a. Mentum flat or nearlyso (Fig. 1), without dorsal premental setae (Fig. 2) -2

Fig.1Fig. 2
Fig. 1:
Ophiogomphusrupinsulensis larva (6x,lateral view), from the Salmon-Trout River, Marquette County,Michigan, by M. F. O'Brien on 21 June 1997. Fig. 2: Aeshna umbrosa larva, (6x, dorsal view).

1b. Prementumand palpal lobes forming spoon-shaped structure (Fig. 3) -4

Fig. 3
Fig. 3. Cordulia shurtleffi larva (6x, lateral view), collected from Lake Genevieve(near Ann Arbor), Washtenaw County, Michigan by M. F. O'Brien on 05April 1998. UMMZODO-1896.

2a.(1a). Antennae 4-segmented, third segment often enlarged(Fig. 4); pro- and metatarsi 2-segmented (Fig. 5); ligula without amedian cleft (Fig. 6) - Gomphidae

Fig. 4 Fig. 5 Fig. 6
Fig. 4:
Ophiogomphusrupinsulensis larva (dorsalview, 12.5x), from Salmon-Trout River, Marquette Co., Michigan,collected by M. F. O'Brien, on 21 June 1997, UMMZODO-1972; Fig. 5-6:Dromogomphusspinosus larva (both 12.5x,ventral view), from Third Sister Lake, Washtenaw Co., Michigan,collected by F. Locke in July, 1940, UMMZODO-0562.

2b. Antennae6- and 7-segmented (Fig. 7); pro- and metatarsi tarsi 3-segmented(Fig. 8); ligula with a median cleft (Fig. 9) - 3

Fig. 7 Fig. 8Fig. 9

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3a.(2b). Antennae segments short, thick, and hairy (Fig.10); prementum with sides sub-parallel in distal three-fifths,abruptly narrowed near base (Fig. 11); a pair of lateral-dorsalabdominal hair tuft present (Fig. 12) - Petaluridae, Tachopteryx thoreyi

Fig.10Fig. 11Fig.12

3b. Antennalsegments slender and bristle-like (picture); prementum widest indistal half, then much narrower in basal half or more (picture);abdomen without lateral-dorsal abdominal hair tufts (picture) -Aeshnidae
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4a.(1b). Distal edge of lateral lobe with large, irregularteeth without associated setae, ligula with a median tooth-like cleft(Fig. x) - Cordulegastridae, Cordulegaster

Fig. x: Cordulegaster maculata larva (6x, ventral view), from Sunset Creek, Iron Co.,Michigan, collected by D. Cuthrell and D. Hyde (Michigan NaturalFeatures Inventory) on 14 June 1996. UMMZODO-1576.

4b. Distaledge of lateral lobe entire, or with even-sized dentations, withassociated setae (picture); ligula not as above (picture) -5

Fig.x Fig. x
Fig. x-x:
Libellulaluctuosa larva (12.5x,ventral view), from Pond at Clear Creek (Norris Dam), Anderson Co.,Tennessee, collected by M. Wright on 21 July 1946.UMMZODO-1994.

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5a.(4b). Head with thick, erect frontal horn postitionedbetween antennae (Fig. x), andmetafemur very long, reaching at leastto apex of abdominal segment 8 (picture); metasternum with broad,median tubercle (picture) - Macromiidae

Fig. xa Fig.xb Fig. xc
Fig. xa: Macromiaillinoiensis larva (Figs.xa-xb, 6x dorsal view; Fig. xc, 6x ventral view), from an unknownlocality in Alpena Co., Michigan, collected by C. L. Hubbs on 30August 1925. UMMZODO-1219. Fig. xb: Macromia illinoiensis larva (6x, dorsal view), same specimen as Fig. xa. Fig.xc: Macromiaillinoiensis larva, (6x,ventral view), same specimen as in Fig. xa.

5b. Headwithout frontal horn positioned between antennae (Fig. x), andmetafemur not reaching apex of abdominal segment 8 (Fig. x);metasternum without median tubercle - 6

Fig. x Fig.x
Fig. xa: Epithecaspinigera larva (6x, dorsalview), from an unknown locality in Montmorency Co., Michigan,collected by C. L. Hubbs in July, 1925. UMMZODO-0310. Fig. xb:Epithecaspinigera larva (12.5x,dorsal view), same specimen as in Fig. xa.

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Artificial key(no one character can reliably separate the families Corduliidae andLibellulidae, hence one may have to run through the keys of bothfamilies to reliably identify a specimen to genus):

6a(5b). Distal edge oflateral lobe of labium with prominent crenations, usually at least asone-fourth deep as wide (fig); cerci usually at least one-half aslong as epiproct (fig); abdomen generally ends abruptly (fig) -7

Fig.xa Fig. xb Fig. xc Fig. xd
Fig. xa:
Epithecacynosura larva (25x, ventralview), from Hess Pond, Columbus, Franklin Co., Ohio, collected by M.Wright on 26 May 1939. UMMZODO-2015. Fig. xb: Epitheca cynosura larva (12.5x, dorsal view), same specimen as in Fig.xa. Fig. xc: Neurocorduliayamaskanensis larva (6x,dorsal view), from Paint River, Iron Co., Michigan, collected by D.Cuthrell and D. Hyde on 19 June 1996. UMMZODO-1783. Fig. xd:Epithecacynosura larva (12.5x, dorsalview), specimen as in Fig. xa.

6b. Distaledge of lateral lobe of labium generally with crenations less thanone-fourth as wide, or obsolete (fig. xa); cerci usually less thanone-half as long as epiproct (fig. xb); abdomen distally more tapered(fig) - Libellulidae

Fig. xa Fig. xb Fig. xc
Fig xa-c:
Libellulaluctuosa larva (6x, dorsalview), from Pond at Clear Creek (Norris Dam), Anderson Co.,Tennessee, collected by M. Wright on 21 July 1946. UMMZODO-1994. Fig.xb: Libellulaluctuosa larva (12.5x, dorsalview), same specimen as in Fig. xa. Fig. xc: Libellula luctuosa larva (12.5x, dorsal view), same specimen as in Fig.xa.

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7a. Lateral spine of Ab8,when present, shorter than middorsal length of Ab9 (Fig. x) -Corduliidae

Fig. x: Epitheca spinigera larva (6x, dorsal view), from an unknown locality inMontmorency Co., Michigan, collected by C. L. Hubbs in July, 1925.UMMZODO-0310.

7b. Lateralspine of Ab8 as long as middorsal length of Ab9, or longer (Fig. x) -Libellulidae, genus Pantala

Fig. x
Fig. x:
Pantalahymenea larva (6x, dorsalview), from Marble Cliffs Pond, Columbus, Franklin Co., Ohio,collected by M. Wright on 03 August 1939. UMMZODO-1540.

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Gloyd, L. K. 1959.Elevation of the Macromia group to family status (Odonata).Entomological News 70(8):197-205.

Walker, E. M.,and P. S. Corbet. 1975. The Odonata of Canada and Alaska, Vol. 3.University of Toronto Press: Toronto. xvi +308 p.

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

Wright, M.,and A. Peterson. 1944. A key to the genera of Anisopterous dragonflynymphs of the United States and Canada (Odonata, SuborderAnisoptera). Ohio Journal of Science44(4):151-166.

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