Aquatic Insects of Michigan

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

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Cordulegastridae (Spiketails) of Michigan - Identification

This family is found in both the Old and New Worlds, but only Cordulegaster is found in North America, with records of five of the eight species of Cordulegaster found in North America having been recorded in Michigan.

C. erronea is appears to be very rare in Michigan, and only one record appears to have 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 C. bilineata and C. 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 is found throughout the state and is by far Michigan's (and Eastern North America's) most common Cordulegaster species, inhabits larger forested creeks and streams with good water quality.

Nymphs are lie-and-wait predators, usually found mostly submerged in sand and silt protected under pieces of large woody or leafy detritus. 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. 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 over the past two decades (e.g., Carle 1983, Lohmann 1992) to place the species of Cordulegaster in an accepted phylogenetic scheme has not yielded universal support. 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, many researchers - especially in North America - are reluctant to accept these proposals (but see May and Carle 1996), and the key below follows the conservative practice of relegating Taeniogaster, Thecophora and Zoraena as subgenera of Cordulegaster (e.g., Westfall and Tennessen 1996). The table below summarizes the placement of Cordulegaster species:

    Species

    North American
    Distribution

    Westfall & Tennessen 1996
    subgenera

    Carle 1983
    genera

    Lohmann 1992
    genera

    C. obliqua

    East

    Taeniogaster

    Taeniogaster

    Taeniogaster

    C. bilineata

    East

    Zoraena

    Zoraena

    Zoraena

    C. diastatops

    East

    Zoraena

    Zoraena

    Zoraena

    C. sayi

    Southeast (FL, GA)

    Zoraena

    Zoraena

    Archegaster

    C. diadema

    West to C. Am.

    Thecophora

    Cordulegaster

    Lauragaster

    C. dorsalis

    West

    Thecophora

    Cordulegaster

    Lauragaster

    C. erronea

    East

    Thecophora

    Cordulegaster

    Kalyptogaster

    C. maculata

    East

    Thecophora

    Cordulegaster

    Panaeagaster

Except for C. bilineata and C. diastatops, separation of the Michigan species of Cordulegaster is relatively straightforward. For those two species, however, morphological descriptions are based on my personal observations and that of Ken Tennessen (personal communication, 2003), but based on a very limited number of observed specimens. Recent work by Pilgrim (2002) has indicated these are good species, at least in the Great Lakes area. Although the two species usually do not occur together (Carle 1983), both species have been found in the same habitat in the northern part of its range.

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

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 Cordulegaster diastatops (Selys)
    b. Metapimeral pale stripe >0.5x as wide as the metapimeron
    3b a. Anteclypeus and legs light brown Cordulegaster 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 wider at base, width at palpal lobes < 2.4x that of basal width 2
    b. Frontal shelf truncate in dorsal view, subacute in lateral view
    c. Lateral spines of Ab8 strongly upcurved
    d. Developing ovipositor of female about 0.7x length of Ab9 sternum
    1b a. Prementum narrower at base, width at palpal lobes > 2.5x that of basal width 3
    b. Frontal shelf appearing rounded in dorsal view, acute and ridge-like in lateral view
    c. Lateral spines of Ab8 not so strongly upcurved
    d. Developing ovipositor of female 0.9x or more the length of Ab9 sternum
    Note: some specimens of C. maculata may have 4 or 6 palpal setae on one palpal lobe (feeding accidents or development flaws?), but almost always 5 setae on the other lobe. In this case, refer to the character on premental setae to determine species.
    2a(1a) a. Labial palp with 4 setae Cordulegaster bilineata (Carle)
    b. Median part of frontal shelf, in dorsal view, quite straight
    c. Anterolateral corner of prothoracic process ("epaulets") nearly square
    d. Inner margin of lateral spines of Ab8-9 straight or nearly so
    e. Stout spines on lateral margins of Ab5-9 long, dark and conspicuous
    2b a. Labial palp with 5 setae Cordulegaster diastatops (Selys)
    b. Median part of frontal shelf, in dorsal view, slightly convex
    c. Anterolateral corner of prothoracic process ("epaulets") nearly more rounded
    d. Inner margin of lateral spines of Ab8-9 concave, tips curving upward
    e. Stout spines on lateral margins of Ab5-9 shorter, pale and inconspicuous
     
    3a(1b) a. Labial palp with 6-7 setae, premental setae 12 or more (usually 8+6) Cordulegaster obliqua (Say)
    b. Developing ovipositor of female about 0.9x length of sternum of Ab9
    3b a. Labial palp with 4-5 setae, premental setae 11 or less (usually 5-6+4-5) 4
    b. Developing ovipositor of female > 1.0x length of sternum of Ab9
     
    4a(3b) a. Labial palp with 4 setae Cordulegaster erronea Hagen in Selys
    b. Few but large obsolescent brown dots on frontal shelf
    c. Prothoracic process ("epaulets") evenly rounded in dorsal aspect
    4b a. Labial palp with 5 setae Cordulegaster maculata Selys
    b. Small round dots numerous, occupying about 1/2 the area of the frontal shelf
    c. Prothoracic process ("epaulets") anteriorlaterally truncated in dorsal aspect, bent posteriorly

References

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.
Pilgrim EM, Roush SA, Krane DE. 2002. Combining DNA sequences and morphology in systematics: testing the validity of the dragonfly species Cordulegaster bilineata. Heredity 89:184-190.
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: Wednesday, February 22, 2017 (EB)