Stylurus Needham,1897 -Hanging Clubtails

Notes -Michigan SpeciesList - Key -References
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Page last updated: 26August 1998 (EB)

Notes on the Michigan Species of Stylurus

Of the eleven species occurring north ofMexico, six species have been collected in Michigan (see maps below).These large, elongate gomphid dragonflies are distinguished fromother Gomphus-complex larvae by the lack of pronounced apical hookson the pro- and mesotibiae. This morphology may be adapted for larvaeto exploit soft substrates where chironomids, tubificids andburrowing mayflies are preyed upon.

Needham's(1897) proposal of the subgenusStylurusfor a species group around G.plagiatus was ultimately raised togeneric level by subsequent workers (Williamson1932, Gloyd 1936, Needham 1948), and has more or less been accepted world-wide(Chao1982; Schmidt 1987; Westfall &Tennessen 1996). Walker (1957, 1958), on the other hand, was hesitant to accept thisdesignation based on similarity of adult genitalia with severalEuropean species of Gomphus,especially G. flavipes. However,Walker acknowledged the morphological characters - includingthose of the larvae and the male genitalia of the adult - thatdistinguish this group from that of other Gomphus. Indeed,Schmidt(1987) eventually synomizedG. flavipes, with which Walker had difficulty, with Stylurus.

S. notatus isfound in sandy substrates of both lakes and rivers throughout thestate, and is probably our most common species of Stylurus. S. scudderi has been foundin the northern part of the lower peninsula and is widespread in theUpper Peninsula. The small S.amnicola has been collected fromstreams and rivers in the UP adjacent to Wisconsin as well as fromseveral other records in the LP. S.laurae and S. plagiatus are knownfrom records in the southern extreme of the state, and Michiganprobably represents the fringe of their North American distribution.The former species is found in sand substrates of smaller streamswith very good water quality, the later is found in both small andlarge streams (free-flowing and impounded) as well as lakes insandy-silt substrate. Though an older record of S. spiniceps is ratherdoubtful (see Kormondy 1958), numerous larval exuviae recently have been found infrom the Huron River watershed in Washtenaw Co., SLP (O'Brien 1997, unpublished information). Larval habitat in theseareas appears to be slow-moving water of larger streams and riverswith silty-sand substrates.

Other links with information on the biology orecology of larval Stylurus:
Toxicitystudy on larvae of S.amnicola in Wisconsin >> http://www.glfc.org/slar95/riass.htm

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MichiganSpecies List

Map1 Map2 Map 3
Map 4Map5 Map 6
Maps 1-6: County distribution of
Stylurus inMichigan
Click on map for a larger image

Stylurus amnicola (Walsh,1862) - Riverine Clubtail - Map1
Stylurus laurae
Williamson,1932 - Laura's Clubtail - Map2
Stylurus notatus
(Rambur, 1842) - Elusive Clubtail - Map 3
Stylurus plagiatus
(Selys, 1854) - Russet-tipped Clubtail - Map 4
Stylurus scudderi
(Selys, 1873) - Zebra Clubtail - Map 5
Stylurus spiniceps
(Walsh, 1862) - Arrow Clubtail - Map 6

Key to Mature Larvae of Michigan Stylurus
(Adopted from K. Tennessen, unpublished information)

1a. Ab9 about 2.0x as long as its basal width (fig);lateral spines of Ab9 3x length of those of Ab8 - S. spiniceps

1b. Ab9 about 1.5x as long as its basal width(fig); lateral spines of Ab9 no more than 2x length of of those ofAb8 - 2


2a(1b). Anterior margin of prementum markedly convex(fig); width of Ab10 1.5-1.8x its length (fig) - S. amnicola

2b. Anterior margin of prementum appearingstraight, at most slightly convex (fig); width of Ab10 < 1.25x itslength (except for S.scudderi) - 3
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3a(2a). Ab9 wide, its width > 1.7x its middorsallength (fig); basal width of lateral spine of Ab9 in dorsal viewabout equal to basal width of spine in lateral view (fig); Ab10 wide,its width greater than or equal to 1.6x its middorsal length (fig) -S. scudderi

3b. Ab9 narrower, its width < 1.4x itsmiddorsal length (fig); basal width of lateral spine of Ab9 in dorsalview clearly narrower than basal width of spine in lateral view(fig); Ab10 narrower, its width < 1.35x its middorsal length (fig)- 4
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4a(3b). Width of Ab9 about 1.3x its length (fig);length of Ab9 1.3-1.4x length of Ab8 (fig); width of Ant3 about 3.5xits width (fig) - S.laurae

4b. Width of Ab9 about 0.9-1.1x its length(fig); length of Ab9 1.4-1.6x length of Ab8 (fig); width of Ant3about 4.5-4.4x its width - 5
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5a(4b). Proximal palpal teeth wider than long (fig);Ab10 wider, middorsal length < 0.9x its width; prementum length ofmature specimens 4.0-4.3mm - S.plagiatus

5b. Proximal palpal teeth as long as wide(fig); Ab10 narrower, middorsal length > 0.9x its width; prementumshorter than above, length of mature specimens 3.4-3.6mm -S. notatus
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References

Chao, H.-f. 1982. Classification of the Chinesedragonflies of the family Gomphidae (Odonata). VI. Entomotaxonomia4(4):287-298.

Gloyd, L. K. 1936.Three new North American species of Gomphinae (Odonata).Occasional Papers of the Museum ofZoology, University of Michigan326:1-18, pls. 1-3 excl.

Huggins, D.G. and W. U. Brigham. 1982. Odonata, pp. 4.1-4.100 in Aquatic Insectsand Oligochaetes of North and South Carolina. A. R. Brigham, W. U.Brigham and A. Gnilka, eds. Midwest Aquatic Enterprises: Mahomet,Illinois.

Kormondy, E. J.1958. Catalogue of the Odonata of Michigan. Miscellaneous Publications of the Museum of Zoology,University of Michigan 104. 43pp.

Needham, J. G. 1897.Preliminary studies of North American Gomphinae. The Canadian Entomologist29:164-168, 181-186 + 1 pl.

Needham, J. G. 1948.Studies on the North American species of the genus Gomphus (Odonata).Transactions of the AmericanEntomological Society73:307-347.

O'Brien, M. F. 1997.Stylurus spiniceps verified for Michigan. Williamsonia1(3):6.

Rambur, J. P. 1842. Histoire naturelledes insectes neuroptères. LibraireEncyclopédique de Roret, Paris. 534 pp.

Schmidt, E. 1987.Generic reclassification of some Westpalaearctic Odonata taxa in viewof their Nearctic affinities (Anisoptera: Gomphidae, Libellulidae).Advances in Odonatology 3:135-145.

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

Selys-Longchamps, M.E. de. 1873. Troisièmes additions. Synopsis des Gomphines.Bulletin de l'Académieroyale des Sciences de Belgique(2)36:491-531.

Schmidt, E. 1987.Generic reclassification of some Westpalaearctic Odonata taxa in viewof their Nearctic affinities (Anisoptera: Gomphidae, Libellulidae).Advances in Odonatology 3:135-145.

Walker, E. M. 1957. The affinities of the North Americanspecies of Gomphus as revealed by the genitalia. Contributions of the Royal Ontario Museum, Division ofZoology and Palaeontology 46. 24pp.

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

Walsh, B. D. 1862.List of the Pseudoneuroptera of Illinois contained in the cabinet ofthe writer, with descriptions of over forty new species, with noteson their structural affinities. Proceedings of the Academy of Natural SciencesPhiladelphia 14:361-402.

Westfall,M. J., Jr. and K. J. Tennessen. 1996. Odonata, pp. 164-211.InMerritt, R. W. and K. W. Cummins (eds.), An Introduction to theAquatic Insects of North America, 3rd Ed. Kendell/ Hunt PublishingCompany: Dubuque, Iowa.

Williamson, E. B.1932. Two new species of Stylurus (Odonata -Gomphinae). Occasional Papers of theMuseum of Zoology, University of Michigan 247. 18 pp. + 1 pl.

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