Stylurus Needham, 1897 - Hanging Clubtails

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

Notes on the Michigan Species of Stylurus

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

Needham's (1897) proposal of the subgenus Stylurus for a species group around G. plagiatus was ultimately raised to generic level by subsequent workers (Williamson 1932, Gloyd 1936, Needham 1948), and has more or less been accepted world-wide (Chao 1982; Schmidt 1987; Westfall & Tennessen 1996). Walker (1957, 1958), on the other hand, was hesitant to accept this designation based on similarity of adult genitalia with several European species of Gomphus, especially G. flavipes. However, Walker acknowledged the morphological characters - including those of the larvae and the male genitalia of the adult - that distinguish this group from that of other Gomphus. Indeed, Schmidt (1987) eventually synomized G. flavipes, with which Walker had difficulty, with Stylurus.

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numerous larval exuviae recently have been found in from the Huron River watershed in Washtenaw Co., SLP (O'Brien 1997, unpublished information).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

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

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Michigan Species List

Map 1 Map 2 Map 3
Map 4 Map 5 Map 6
Maps 1-6: County distribution of
Stylurus in Michigan
Click on map for a larger image

Stylurus amnicola (Walsh, 1862) - Riverine Clubtail - Map 1
Stylurus laurae
Williamson, 1932 - Laura's Clubtail - Map 2
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 of Ab8 - 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 appearing straight, at most slightly convex (fig); width of Ab10 < 1.25x its length (except for S. scudderi) - 3
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3a(2a). Ab9 wide, its width > 1.7x its middorsal length (fig); basal width of lateral spine of Ab9 in dorsal view about 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 its middorsal length (fig); basal width of lateral spine of Ab9 in dorsal view 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 3.5x its 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 Ant3 about 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 of mature specimens 4.0-4.3mm - S. plagiatus

5b. Proximal palpal teeth as long as wide (fig); Ab10 narrower, middorsal length > 0.9x its width; prementum shorter than above, length of mature specimens 3.4-3.6mm - S. notatus
Back to previous couplet (4); Back to beginning of key

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References

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

Gloyd, L. K. 1936. Three new North American species of Gomphinae (Odonata). Occasional Papers of the Museum of Zoology, University of Michigan 326:1-18, pls. 1-3 excl.

Huggins, D. G. and W. U. Brigham. 1982. Odonata, pp. 4.1-4.100 in Aquatic Insects and 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. 43 pp.

Needham, J. G. 1897. Preliminary studies of North American Gomphinae. The Canadian Entomologist 29:164-168, 181-186 + 1 pl.

Needham, J. G. 1948. Studies on the North American species of the genus Gomphus (Odonata). Transactions of the American Entomological Society 73:307-347.

O'Brien, M. F. 1997. Stylurus spiniceps verified for Michigan. Williamsonia 1(3):6.

Rambur, J. P. 1842. Histoire naturelle des insectes neuroptères. Libraire Encyclopédique de Roret, Paris. 534 pp.

Schmidt, E. 1987. Generic reclassification of some Westpalaearctic Odonata taxa in view of 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 des Sciences de Belgique 21:23-114.

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

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

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

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

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

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

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

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