Notes - Key - References
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Page last updated: 29 June 1998 (EB)
Notes on the Anisoptera
The 113 species of dragonflies so far recorded
in Michigan are divided into 7 families and 36 genera. The larvae of
Anisoptera are distinguished from that of Zygoptera by a more robust
shape, such that the thorax and abdomen are generally wider than the
head, and that respiration chiefly occurs by expansion and
contraction of abdominal muscles that move water in and out of the
rectal chamber across gills located within this structure. This also
permits larvae to achieve rapid bursts of speed in the water. Larvae
of Michigan Anisoptera inhabit just about every type of aquatic
ecosystem in the state, from the largest of lakes to the smallest bog
pool, from the very small woodland seeps to the largest of our
rivers. Our species of Cordulegaster generally are found only in
seeps and streams, and the only species of Petaluridae found in
Michigan - Tachopteryx thoreyi
- probably is found only in leafy
material in the upper portions of forested seeps, and is probably our
only odonate that can breathe air (semiterrestrial).
The similarity in morphology among the larvae of Libellulidae,
Corduliidae and Macromiidae has led some to group these as
subfamilies in Libellulidae. As of yet, no one morphological
character has been found to reliably separate larvae of Corduliidae
from Libellulidae, although characters suggested by Walker and Corbet
(1975) and Westfall and
Tennessen (1996) - cerci at least 0.5x
the 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 of
Macromiidae as a family is not yet clear, and many authorities retain
it as a subfamily of Corduliidae (e.g., Westfall and
Tennessen 1996). Certain larval (and adult) characters, however,
separate these larvae from both Corduliidae and Libellulidae (see
Gloyd
1959). Hopefully a thorough
morphological, molecular and ecological study of the entire group
will one day resolve the matter.
1a. Mentum flat or nearly so (Fig. 1), without dorsal premental setae (Fig. 2) - 2
Fig.
1
Fig. 2
Fig. 1: Ophiogomphus
rupinsulensis 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. Prementum and 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 05
April 1998. UMMZODO-1896.
2a.(1a). Antennae 4-segmented, third segment often enlarged
(Fig. 4); pro- and metatarsi 2-segmented (Fig. 5); ligula without a
median cleft (Fig. 6) - Gomphidae
Fig. 4
Fig. 5
Fig. 6
Fig. 4: Ophiogomphus
rupinsulensis larva (dorsal
view, 12.5x), from Salmon-Trout River, Marquette Co., Michigan,
collected by M. F. O'Brien, on 21 June 1997, UMMZODO-1972; Fig. 5-6:
Dromogomphus
spinosus larva (both 12.5x,
ventral view), from Third Sister Lake, Washtenaw Co., Michigan,
collected by F. Locke in July, 1940, UMMZODO-0562.
2b. Antennae 6- and 7-segmented (Fig. 7); pro- and metatarsi tarsi 3-segmented (Fig. 8); ligula with a median cleft (Fig. 9) - 3
Fig. 7
Fig. 8
Fig. 9
Back to beginning of
key
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-dorsal
abdominal hair tuft present (Fig. 12) - Petaluridae, Tachopteryx thoreyi
Fig.
10
Fig. 11
Fig.
12
3b. Antennal
segments slender and bristle-like (picture); prementum widest in
distal half, then much narrower in basal half or more (picture);
abdomen without lateral-dorsal abdominal hair tufts (picture) -
Aeshnidae
Back to previous couplet
(2); Back to beginning of
key
4a.(1b). Distal edge of lateral lobe with large, irregular
teeth 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 Natural
Features Inventory) on 14 June 1996. UMMZODO-1576.
4b. Distal edge of lateral lobe entire, or with even-sized dentations, with associated setae (picture); ligula not as above (picture) - 5
Fig.
x
Fig. x
Fig. x-x: Libellula
luctuosa 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.
Back to beginning of
key
5a.(4b). Head with thick, erect frontal horn postitioned
between antennae (Fig. x), and
metafemur very long, reaching at least
to apex of abdominal segment 8 (picture); metasternum with broad,
median tubercle (picture) - Macromiidae
Fig. xa
Fig.
xb
Fig. xc
Fig. xa: Macromia
illinoiensis larva (Figs.
xa-xb, 6x dorsal view; Fig. xc, 6x ventral view), from an unknown
locality in Alpena Co., Michigan, collected by C. L. Hubbs on 30
August 1925. UMMZODO-1219. Fig. xb: Macromia illinoiensis larva (6x, dorsal view), same specimen as Fig. xa. Fig.
xc: Macromia
illinoiensis larva, (6x,
ventral view), same specimen as in Fig. xa.
5b. Head without frontal horn positioned between antennae (Fig. x), and metafemur not reaching apex of abdominal segment 8 (Fig. x); metasternum without median tubercle - 6
Fig. x
Fig.
x
Fig. xa: Epitheca
spinigera larva (6x, dorsal
view), from an unknown locality in Montmorency Co., Michigan,
collected by C. L. Hubbs in July, 1925. UMMZODO-0310. Fig. xb:
Epitheca
spinigera larva (12.5x,
dorsal view), same specimen as in Fig. xa.
Back to previous couplet
(4); Back to beginning of key
Artificial key
(no one character can reliably separate the families Corduliidae and
Libellulidae, hence one may have to run through the keys of both
families to reliably identify a specimen to genus):
6a(5b). Distal edge of lateral lobe of labium with prominent crenations, usually at least as one-fourth deep as wide (fig); cerci usually at least one-half as long as epiproct (fig); abdomen generally ends abruptly (fig) - 7
Fig.
xa
Fig. xb
Fig. xc
Fig. xd
Fig. xa: Epitheca
cynosura larva (25x, ventral
view), 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: Neurocordulia
yamaskanensis 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:
Epitheca
cynosura larva (12.5x, dorsal
view), specimen as in Fig. xa.
6b. Distal edge of lateral lobe of labium generally with crenations less than one-fourth as wide, or obsolete (fig. xa); cerci usually less than one-half as long as epiproct (fig. xb); abdomen distally more tapered (fig) - Libellulidae
Fig. xa
Fig. xb
Fig. xc
Fig xa-c: Libellula
luctuosa larva (6x, dorsal
view), from Pond at Clear Creek (Norris Dam), Anderson Co.,
Tennessee, collected by M. Wright on 21 July 1946. UMMZODO-1994. Fig.
xb: Libellula
luctuosa larva (12.5x, dorsal
view), same specimen as in Fig. xa. Fig. xc: Libellula luctuosa larva (12.5x, dorsal view), same specimen as in Fig.
xa.
Back to previous couplet
(5); Back to beginning of key
7a. Lateral spine of Ab8,
when present, shorter than middorsal length of Ab9 (Fig. x) -
Corduliidae
Fig.
x
Fig. x: Epitheca spinigera larva (6x, dorsal view), from an unknown locality in
Montmorency Co., Michigan, collected by C. L. Hubbs in July, 1925.
UMMZODO-0310.
7b. Lateral spine of Ab8 as long as middorsal length of Ab9, or longer (Fig. x) - Libellulidae, genus Pantala
Fig. x
Fig. x: Pantala
hymenea larva (6x, dorsal
view), from Marble Cliffs Pond, Columbus, Franklin Co., Ohio,
collected by M. Wright on 03 August 1939. UMMZODO-1540.
Back to previous couplet (6); Back to beginning of key
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 An Introduction 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 dragonfly nymphs of the United States and Canada (Odonata, Suborder Anisoptera). Ohio Journal of Science 44(4):151-166.