Michigan's second largest family of dragonflies, 30 species in 10 genera have so far been recorded in our state. The taxonomic status of one genus, Gomphus, has been disputed, but it looks like the names are stabilized under the latest work by Ware, et. al (2016), and Gomphus sensu stricto is an old-world genus, with the North American subgenera elevated to generic status. I have made the changes in this 2017 update accordingly. Erpetogomphus has not yet been recorded in Michigan, but a record from central Ohio may make it possible that it can be encountered in the southernmost part of our state.
Although adults are referred to as "clubtails," as the abdomen is often enlarged posteriorly to resemble a club, gomphids could just as easily be called "burrowing dragonflies," in reference to the larval habit of burrowing into various substrates in lotic and lentic waters. Their larval morphology - reduced antennae segments and strong fossorial legs, among other morphological adaptations - is ideally suited for concealing themselves in substrate and loose particulate debris. It's very interesting to watch live captured individuals, when released or put into a container filled with silt, sand or other debris, quickly use their legs to conceal themselves. Most are found in silt, sand or gravel in lakes and rivers, but one species - Hagenius brevistylus - has adapted itself to conceal itself by sprawling within leafy and woody debris in streams and lakes.
1a. Mesocoxae closer
together than procoxae (Fig.1a1); Ant4 elongate, 0.25x as long as
antennal segment 3 (Fig.1a2) - Progomphus
1b. Mesocoxae not closer together than procoxae (picture); antennal segment 4 vestigial or a small, rounded knob (picture) - 2
2a.(1b). Abdomen subcircular, body very flat (Fig. 2a1); head with paired tubercles behind eyes (picture) - Hagenius brevistylus
2b. Abdomen not so flat, more cylindrical (picture); head without paired tubercles behind eyes (picture) - 3
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3a.(2b). Wing cases strongly divergent (Fig. 3a1); Ab8 and 9 about equal in middorsal length; lotic - 4
Fig. 3a1: Ophiogomphus rupinsulensis larva, 12x dorsal view. Specimen collected from the Salmon-Trout River, Marquette County, Michigan, by M. F. O'Brien on 21 June 1997.
3b. Wing cases
parallel along back (picture); middorsal length of Ab9 clearly longer
than that of Ab8 - 5
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4a.(3a). Epiproct, cerci and paraprocts all subequal in length (picture) - Erpetogomphus designatus
4b. Cerci distinctly shorter, at most 0.8x the length of the epiproct and paraprocts (Fig. 4b1) - Ophiogomphus
Fig. 4b1: O. susbehcha exuvia (12.5x, lateral view), from St. Croix River, Burnett Co., WI, collected by T. E. Vogt on 30 May 1990.
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couplet(3); Back to beginning of
5a.(3b). Flattened antennal segment 3 nearly oval (Fig. 5a1); lotic - Stylogomphus albistylus
Fig. 5a1. Stylogomphus albistylus larva, collected from Mountain Stream, Marquette Co., Michigan, USA, on 30 June 1996 by Bright, O'Brien and M. A. Kielb. UMMZODO-0179.
Cylindrical antennal segment 3 more than 4 times as long as wide
(picture) - 6
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6a.(5b). Abdominal segment 9 with a long acute middorsal ridge ending in a long, sharp apical hook usually markedly darker than body base color (Fig. 6a1), ridge raised in lateral view (Fig. 6a2) - Dromogomphus spinosus
Fig. 6a1 Fig.
Fig. 6a1: Dromogomphus spinosus larva (12x, dorsal view), collected from Third Sister Lake, outside Ann Arbor in Washtenaw County, Michigan, by F. Locke, on July 1940. UMMZODO-0562.
Fig. 6a2: Ibid, lateral view. Both images taken at 12x. UMMZODO-0562.
segment 9 without such an acute, dark middorsal ridge bearing dorsal
hook at apex (picture), and usually not markedly raised in lateral
view (picture) - 7
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7a.(6b). Pro- and mesotibiae with burrowing hooks absent or obsolete (picture); lotic - Stylurus
7b. Pro- and
mesotibiae with burrowing hooks at outer apical angle about as long
as width of tarsus (picture) - 8
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8a.(7a). Abdominal segment 10 longer than wide (Fig. 8a1-2) - Arigomphus
Fig 8a1: Arigomphus cornutus exuvia, (12.5x, dorsal view) from Washtenaw Co., Michigan, collected 23 May 1998 by M. F. O'Brien.
segment 10 wider than long (picture) - Gomphus complex
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