Dromogomphus Selys1854 -Spinylegs


Fig. 1: Dromogomphus spinosus, exuvia, from Ives Lake, Marquette Co.,Michigan,
collected by M. F. O'Brien on 02 July 1996. UMMZODO-1247

Notes -Michigan SpeciesList - References
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Page last updated: 17July 1998 (EB)

Notes on the Michigan larvae of Dromogomphus

Of the three species of this eastern NorthAmerican genus, only one - D.spinosus (Fig. 1) - has been recordedin Michigan (Map 1, below). However, the adults of D. spoliatus have beenrecorded in northwestern Ohio, and exuviae collected in northernIndiana by E. B. Williamson in 1907 (Wright 1946), thus this species may possibly be found in southernMichigan and is included in the key below.


Map 1: County distribution ofDromogomphusspinosus in Michigan
Click on map for a larger image

Westfall andTennessen (1979) expand on Wright's (1946) older work to provide the most recent taxonomictreatment for the genus. These are large (last instars usuallymeasure about 32-35 mm), elongate gomphid larvae, distinctive fortheir large, dark mid-dorsal abdominal spines, and this characterwill help distinguish this species from larvae of Gomphus graslinellus andG. lividusto which there is some resemblance. The dark mid-dorsal abdominalridge and spines usually are clearly distinguished from the lighterground color of the abdominal segment, and this color in larvae andexuviae often remains after long-term preservation in alcohol (pers.obs.).

Larvae can be fairly common in rocky lakemargins as well as large rivers and stream rapids. Walker (1958) remarks that this species is the most common latesummer gomphid of large streams and lakes in southern Ontario. Larvaeapparently crawl several feet from the water's edge upon a log orrock to emerge. Very little is known about the ecology or biology ofthis genus. In Michigan, adults appear to emerge from mid-Junethrough July, based on observations from F. Locke (July 1940,Washtenaw Co.), E. J. Kormondy (25 June 1953, Douglas Lake, CheboyganCo.), T. Nowicki (28 June 1997, Green Lake, Benzie Co.) and E. Bright(27 June 1996, Ives Lake, Marquette Co.).

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MichiganSpecies List

Dromogomphus spinosusSelys,1854 - Black-shouldered Spinyleg
*Dromogomphus spoliatus (Hagenin Selys, 1858) - Flag-tailedSpinyleg

*Not recorded in Michigan, but may beencountered in the southern LP

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Key to the Mature Larvae ofDromogomphus
(References:
Wright1946 and Westfall andTennessen 1979)

1a. Mid-dorsalprocesses on abdominal segments 5- or 6-9 (Fig. 2); lateral spines onabdominal segment 9 about 1.5x the length of those on segment 8 (Fig.3); small, stout spines along lateral margins of abdominal segments7, 8 and 9 (Fig. 4); end tooth of palpal lobe 2.0x as long as smallerteeth next to it (Fig. 5) - D.spinosus

Fig. 2 Fig.3 Fig. 4 Fig. 5
Fig. 2: (6x, dorsal view), Dromogomphus spinosus larva, from Third Sister Lake, Washtenaw Co., Michigan,collected by F. Locke in July 1940. UMMZODO-0562. Fig. 3: (12.5x,dorsal view): Dromogomphusspinosus exuvia, from IvesLake, Marquette Co., Michigan, collected by M. F. O'Brien on 02 July1996. UMMZODO-1247; Fig. 4: (12.5x, dorsal view), Dromogomphus spinosus larva, from Third Sister Lake, Washtenaw Co.,Michigan, collected by F. Locke in July 1940. UMMZODO-0562.; Fig. 5:(25x, ventral view), Dromogomphus spinosus larva, from Third Sister Lake, Washtenaw Co., Michigan,collected by F. Locke in July 1940. UMMZODO-0562.

1b. Mid-dorsalprocesses on abdominal segments 8 and 9, absent on segments 5, 6 and7 (Fig. 6); lateral spines on abdominal segment 9 about 3.0x as longas those on segment 8 (Fig. 7); small, stout spines along lateralmargins of abdominal segment 9, sometimes along segment 8, but absentalong segment 7 (Fig. 8); end tooth of palpal lobe less than 2.0x aslong as smaller teeth next to it (Fig. 9) - D. spoliatus

Fig. 6 Fig. 7 Fig. 8 Fig. 9
Figs. 6 (6x, dorsal view), 7 (12.5x, dorsal view), 8 (12.5x, dorsalview) and 9 (25x, ventral view):
Dromogomphus spoliatus exuvia, from Fort Wayne, Allen Co., Indiana, collectedby E. B. Williamson on 03 August 1902. UMMZODO-1597.

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References

Selys-Longchamps, M.E. de. 1854. Synopsis des Gomphines. Bulletin de l'Académie royale des Sciences deBelgique 21:23-114.

Selys-Longchamps, M.E. de. 1858. Monographie des Gomphines. Mémoires de la Société Royale desSciences de Liége 9:1-460, 23pls. (Note: some authors reference this work as being published in1857. The copy here in the E. B.Williamson Library, UMMZ, has apublished date in the frontpiece as "Novembre 1857," but thesupplemental plates at the end of the work, by H. A. Hagen, areclearly dated 1858).

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

Westfall,M. J., Jr. and K. J. Tennessen. 1979. Taxonomic clarification withinthe genus Dromogomphus Selys (Odonata: Gomphidae). The Florida Entomologist 62(3):266-273.

Wright, M. 1946.Taxonomic notes on the nymphs of the dragonfly genus Dromogomphus Selys.Journal of the Tennessee Academy ofScience 21:183-186.

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