Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

Cordulegastridae (Spiketails) of Michigan - Identification

This family is found in both the Old and New Worlds, with records of five of the 10 species found in North America having been recorded in Michigan. These are beautiful and large black or brown dragonflies with bold yellow stripes and spots on the thorax as well as abdominal segments. Nymphs are lie-and-wait predators, usually found mostly submerged in sand and silt protected under pieces of large woody or leafy detritus. Their large, jagged-like teeth on the palpi are a distinctive character for the family.

C. erronea appears to be very rare in Michigan, with only one record having been reported from the western part of the LP. This is mostly a southern species, and Michigan probably represents the northernmost (accidental?) part of its range. This species is on the State's Special Concern List. In south-central Ohio (Hocking Co.), C. erronea inhabits sand substrates of forested seeps and spring-fed brooks with considerable slope (Dan Riggs, personal communication). C. obliqua tends to be found only in first-order, small sandy forest brooks, at least in the southern part of its range (Tennessen et al. 1995). Based on observations of adult Z. bilineata and Z. diastatops in Michigan, habitat tends to be sandy substrates of downstream pools and runs of hillside springs and brooks, both in forested as well as open or bushy pastures. This appears to agree with habitat descriptions for these species from other workers (e.g., Walker 1958, Tennessen et al. 1995). The rarity of specimens (particularly nymphs) from our state reflects insufficient sampling of these habitats. Conversely, C. maculata, which inhabits larger forested creeks and streams with good water quality, is found throughout the state and is Michigan's (and Eastern North America's) most common cordulegastrid species.

These species are long-lived and probably require at least three years in which to develop into adults, at least in the northern part of its range: three different size classes of larval C. maculata have been found in streams from Marquette Co., UP (pers. obs.). Emergence of this species in the north appears to occur in early to mid-June, with females observed ovipositing in early July. Adults tend not to stray too far from their aquatic habitats. Emergence occurs close to the waters edge, usually in June. Johnson (1982) studied prey selection of C. maculata from a stream in the Adirondack Mountains in New York, USA., and found that mayflies (Baetis sp. and Paraleptophlebia sp.) were the principal prey, with chironomids, simulids and caddisflies of various trophic relationships also important components. The author speculated that C. maculata in this stream are active foragers (apparently at night), as their principal prey (in this study, the mayflies) where not well represented in Surber samples that were used to collect nymphs in the deeper sections of the stream. Unfortunately, the author did not account for drift in prey species, thus the observation must be considered speculative.

Work since the 1980s (e.g., Carle 1983, Lohmann 1992, Bechly 1996) to place the species of Cordulegaster within an accepted phylogenetic scheme has not yielded universal support, particularly from workers in North Americca (e.g., Glotzhober 1997, Needham et al. 2014, Paulson 2011). In describing Zoreana bilineata, Carle (1983) elevates to genus the subgenera Cordulegaster (or Thecophora), Taeniogaster and Zoraena. Going even further, Lohmann (1992) argues that Cordulegaster is an Old World genus, and that the North American species are surviving and individual remnants of formerly speciose, distinct ancient groups. He grouped the eight North American species into the six genera (see table below). However, some researchers are reluctant to accept these proposals (but see May and Carle 1996). Only a comprehensive survey combining molecular and taxonomic evidence from all extant species may help to lead to an eventual concensus. A recent synopsis by Tennessen (2019) of nymphal characters supports the generic separation of Cordulegasterand Zoraena, and this separation is followed in the keys below. The table below summarizes the placement of North American Cordulegaster species:

Species	North American Distribution	Westfall & Tennessen 1996 subgenera	Carle 1983 genera	Lohmann 1992 genera	Tennessen 2019 genera
C. obliqua	East	Taeniogaster	Taeniogaster	Taeniogaster	Cordulegaster
C. bilineata	East	Zoraena	Zoraena	Zoraena	Zoraena
C. diastatops	East	Zoraena	Zoraena	Zoraena	Zoraena
C. sayi	Southeast (FL, GA)	Zoraena	Zoraena	Archegaster	Zoraena
C. diadema	West to C. Am.	Thecophora	Cordulegaster	Lauragaster	Cordulegaster
C. dorsalis	West	Thecophora	Cordulegaster	Lauragaster	Cordulegaster
C. erronea	East	Thecophora	Cordulegaster	Kalyptogaster	Cordulegaster
C. maculata	East	Thecophora	Cordulegaster	Panaeagaster	Cordulegaster
C. sarracenia	South				Zoraena
C. talaria	South				Zoraena

Taxonomic References: Carle 1983, Lohmann 1992, Needham et al. 2014, Paulson 2011, Tennessen 2019, Walker 1958

Adults

1a	a. Occiput raised medially in a conical eminence, posterodorsal portions of head denticulate	Cordulegaster obliqua (Say)
	b. Ab3-7 with a middorsal, spear- or arrow-shaped spots
1b	a. Occiput evenly convex, posterodorsal portions of head not denticulate	2
	b. Ab3-7 without middorsal spearhead-shaped yellow dots, but either with almost complete tergal bands, paired dorsolateral spots, or subcircular or bilobed middorsal spots
2a(1b)	a. Compound eyes separated dorsally, head distinctly bulged behind compound eyes	3
	b. Male epiproct shorter than wide
	c. Female ovipositor extending beyond the end of the abdomen 1/3x or less its length
2b	a. Compound eyes contiguous at one median point, head not distinctly bulged behind compound eyes	4
	b. Male epiproct longer than wide
	c. Female ovipositor extending beyond the end of the abdomen for at least 1/2x its length
3a(2a)	a. Anteclypeus and legs black	Zoraena diastatops (Selys)
	b. Metapimeral pale stripe >0.5x as wide as the metapimeron
3b	a. Anteclypeus and legs light brown	Zoraena bilineata (Carle)
	b. Metapimeral pale stripe <0.5x as wide as the metapimeron
4a(2b)	a. Terga of Ab2-8 nearly encircled by bands of yellow	Cordulegaster erronea Hagen in Selys
	b. Antefrons dark brown
	also: Cubito-anal crossveins 3 or 4, rarely 2; rare of head mostly black or brown; Ab10 black, unmarked with yellow
4b	a. Terga of Ab2-8 with yellow dorsolateral spots	Cordulegaster maculata Selys
	b. Antefrons predominantly yellow
	also: Entire postfrons decidedly darker than antefrons; forewing with 3 cubito-anal crossveins; abdomen usually with dorsolateral spots separated middorsally

Mature Nymphs

1a	a. Prementum in ventral view with basal transverse suture V-shaped, ventromedial groove usually originating distal to base	Cordulegaster, 2
	b. Dorsolateral rim of palpus with longest marginal setae length 2.0-3.5x width of a primary setal base
	c. Frontal ridge with 2-4 scattered piliform setae at most amongst stouter setae
	d. Ab8 posterolateral spine, if present, curved upward slightly, tip directed toward Ab9 spine
1b	a. Prementum in ventral view with basal transverse suture nearly straight across, ventromedial groove originating close to base	Zoraena, 4
	b. Dorsolateral rim of palpus with longest marginal setae length 1.0-1.5x width of a primary setal base
	c. Frontal ridge with medial tuft of 8-12 piliform setae amongst stouter setae
	d. Ab8 posterolateral spine markedly curved upward, tip directed dorsad of Ab9 spine
2a(1a)	a. Palpal setae 4	Cordulegaster erronea Hagen in Selys
	b. Marginal setae of frontal ridge rectangular to fan-shaped, short (0.08-0.40 mm)
	c. Dorsum of body beset mostly with small, dark, flat setae and relatively few piliform setae (e.g., on mesopleurae)
2b	a. Palpal setae usually 5-8	3
	b. Marginal setae of frontal ridge acuminate to blunt apically, elongate, longer (0.40-0.80 mm)
	c. Dorsum of body beset mostly with pale, piliform setae and/or short dark acuminate setae (e.g., on mesopleurae)
3a(2b)	a. Palpal setae usually 5, occasionally 4 or 6 on one side (rarely 6 on both sides)	Cordulegaster maculata Selys
	b. All marginal setae of frontal ridge pale
	c. Costal margin of wing sheaths with long pale setae only
	d. Prementum usually with 5-6 primary setae on each side, sometimes 7 on one or both sides
3b	a. Palpal setae 6 per side,l sometimes 7 or 8 on one side	Cordulegaster obliqua (Say)
	b. Some marginal setae of frontal ridge dark
	c. Costal margin of wing sheaths with both long and short dark setae
	d. Prementum with 7 or 8 primary setae on each side, rarely 6
4a(1b)	a. Ab3-8 tergites with many short, fan-shaped setae interspersed with few slender setae	Zoraena diastatops (Selys)
	b. Posterior margin of Ab8-10 sternites beset mostly with flat, truncate setae
	c. Palpal setae usually 5 per side
4b	a. Ab3-8 tergites with only piliform setae, or with a few flat setae interspersed with slender setae	Zoraena bilineata (Carle)
	b. Posterior margin of Ab8-10 sternites beset mostly with sharply pointed setae
	c. Palpal setae usually 4 per side

References

Bechly G. 1996. Morphologische Untersuchungen am Flügelgeäder der rezenten Libellen und deren Stammgruppenvertreter (Insecta; Pterygota; Odonata) unter besonderer Berücksichtigung der Phylogenetischen Systematik und des Grundplanes der Odonata. Petalura, Spec. Vol. 2. 402 p, 3 tabls, 111 figs.
Carle FL. 1983. A new Zoraena (Odonata: Cordulegastridae) from Eastern North America, with a key to the adult Cordulegastridae of America. Annals of the Entomological Society of America 76(1):61-68.
Johnson JH. 1982. Diet composition and prey selection of Cordulegaster maculata Sel. larvae (Anisoptera: Cordulegasteridae). Notulae Odonatologicae 1(9):151-153.
Kennedy CH. 1917. Notes on the life history and ecology of the dragonflies (Odonata) of central California and Nevada. Proceedings of the United States Museum 52:483-635.
Lohmann H. 1992. Revision der Cordulegastridae. 1. Entwurf einer neuen Klassifizierung der Familie (Odonata: Anisoptera). Opuscula Zoologica Fluminen 96:1-18.
May ML., Carle FL. 1996. An annotated list of the Odonata of New Jersey, with an appendix on nomenclature in the genus Gomphus. Bulletin of American Odonatology 4(1):1-35.
Needham JG, Westfall MJ, May ML. 2014. Dragonflies of North America, Third Edition. Scientific Publishers, Gainesville, Florida, USA. xiv + 657 p.
Paulson D. 2011. Dragonflies and damselflies of the East. Princeton Field Guides. Princeton University Press, Pinceton, New Jersey, USA. 538 p.
Tennessen KJ. 2019. Dragonfly nymphs of North America: An Identification Guide. Springer International Publishing, Cham, Switzerland: xiv + 620 p.
Walker EM. 1958. The Odonata of Canada and Alaska, Vol. 2. University of Toronto Press: Toronto.
Westfall MJ, Tennessen KJ. 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.

Page created: Augst 20, 1998 (From Odonata Larvae of Michigan) - Last updated: Friday, April 24, 2020 (EB)