Aquatic Insects of Michigan

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

Tramea (Libellulidae) (Gliders) of Michigan - Identification

There are seven species of Tramea in North America, four of which have been found in our state. Like those of Pantala, adults are large, wide-ranging migratory fliers that are noticeably marked with bands of brown across the base of the hindwing. Two species, T. carolina (southern) and T. lacerata (widespread), are well-documented in our state, and the third, T. calverti, is principally Neotropical but has been recently been documented as perhaps an accidental occurrence due to a weather system, or reflecting changing distribution patterns (Craves and O'Brien 2011). Like other migratory dragonfly species, nymphs can develop in short periods of time and can thrive in temporory bodies of water. T. lacerata is found in open marshy lagoons and bays, probably does not overwinter in the larval stage in the morthernmost localities where adults have been recorded. Nymphs were taken in southern Utah from a spring pond containing watercress and other aquatic plants with trees and bushes surrounding the pond; but elsewhere nymphs may occupy ponds without surrounding trees (Musser 1962). T. carolina is found in clear waters of ponds and small lakes, especially those with rooted, submerged vegetation, and occasionally in quiet streams. Bick (1950) found nymphs from standing water in mud-bottomed ponds.

Taxonomic references: Needham et al. 2010, Paulson 2011, Tennessen 2019, Walker and Corbet 1975

Adults

1a	a. Dark band at base of hindwing extending outward only about halfway to the proximal angle of the triangle, its outer edge nearly straight	Tramea calverti Muttkowski
	also: Sides of pterothorax with two wide pale stripes on a dark background
1b	a. Dark band at base of hindwing extending outward further, at least to the distal angle of the triangle, its outer edge jagged	2
2a(1b)	a. Blackish species, body and dark band at base of hindwing black	Tramea lacerata Hagen
	b. Hamule not extending beyond the apex of the genital lobe
	c. Cerci 2x as long as epiproct
	d. Subgenital plate about 0.5x as long as the sternum of Ab9
2b	a. Reddish-brown species, body reddish brown and dark band at base of hindwing brown or reddish	3
	b. Hamule extending beyond the apex of the genital lobe
	c. Cerci <2x as long as epiproct
	d. Subgenital plate about 0.6x or more as long as the sternum of Ab9
3a(2b)	a. Dark band at base of the hindwing generally covering the entire anal loop	Tramea carolina (Linnaeus)
	b. Hamules each extending only slightly beyond the apex of the genital lobe
	c. Subgenital plate about 2/3x the length of the sternum of Ab9
3b	a. Dark band at base of the hindwing not covering the distal portion of the anal loop	Tramea onusta Hagen
	b. Hamules each extending about 1/3x their length beyond the apex of the genital lobe
	c. Subgenital plate about as long as the sternum of Ab9

Mature Nymphs (note: It is unlikely there are any breeding populations of Tramea calverti in our state.)

1a	a. Ab7-8 middorsum with numerous closely-spaced, minute spiniform setae, density about 25-40 p/mm2, and Ab6-9 posterior margins usually with only 3-6 preapical long piliform setae, their bases pale, not forming a discernable row	Tramea calverti Muttkowski
	b. Palpal setae usually < 10 (rarely 10)
1b	a. Ab7-8 middorsum with 0 or few (2-15) minute spiniform setae, widely spaced if present, and Ab6-9 posterior margins usually with 10-20 preapical long piliform setae, their bases surrounded by brown marking, forming a distinct row	2
	b. Palpal setae usually >10 or more
2a(1b)	a. Ratio of Ant4 length : Ant3 length ≥0.70	Tramea carolina (Linnaeus)
	b. Pale middorsal mark on Ab8-9 a narrow line
	c. Antennal length usually >5.0 mm
2b	a. Ratio of Ant4 length : Ant3 length <0.70	3
	b. Pale middorsal mark on Ab8-9 an oval, nearly as wide as length of segment
	c. Antennal length usually <5.0 mm
3a(2b)	a. Epiproct length 2.30-3.00 mm, ratio of epiproct length : ventral paraproct length 0.95-1.08	Tramea lacerata Hagen
	b. Ratio of Ab8 posterolateral spine length : Ab9 posterolateral spine length 0.73-0.89
	c. Basal width of Ab9 posterolateral spine 0.64-0.75 mm
3b	a. Epiproct length 1.90-2.30 mm, ratio of epiproct length : ventral paraproct length 0.95-1.08	Tramea onusta Hagen
	b. Ant4 about 2/3x as long as Ant3≤
	c. Basal width of Ab9 posterolateral spine 0.44-0.55 mm

Bick GH. 1950. The dragonflies of Mississippi (Odonata: Anisoptera). American Midland Naturalist 43:66-78.
Craves JA, O'Brien D. 2011. Tramea calverti (Odonata: Libellulidae): New for Michigan with notes on other new reports for the Great Lakes Region. The Great Lakes Entomologist 44(1-2):78-82.
Musser RJ. 1962. Dragonfly nymphs of Utah (Odonata: Anisoptera). University of Utah Biological Series 12(6):1-66.
Needham JG, Westfall MJ, May ML. 2010. 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, Corbet JS. 1975. The Odonata of Canada and Alaska, Vol. 3. University of Toronto Press: Toronto, Ontario. xvi + 308.

Page created: July 17, 1998 - Last updated: April 22, 2020 (EB)