Aquatic Insects of Michigan

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

Macromiidae (Cruisers) of Michigan - Identification

Mature nymphs are large sprawlers in loose substrates, distinctive for their very long, slender legs with simple, slender long tarsal claw, and oval, broad abdomens adorned with sharp, cultriform dorsal hooks. Nymphs are frequently found in larger streams as well as channels and lakes. They are absent from stagnant waters. Members of this family are most diverse in warmer regions of the world, with a few species extending into colder regions. Four species in two genera of Macromiidae are found in Michigan: Macromia illinoiensis and Didymops transversa are commonly encountered in most parts of the state, with Macromia taeniolata and Macromia alleghaniensis less commonly encountered in the southern LP.

Taxanomic references (Needham et al. 2014, Tennessen 2019)

Adults

1a	a. Nodus of forewing about midway between base and apex of wing	Didymops transversa (Say)
	b. Vertex simple, rounded, smaller than occiput, which has a bulbous swelling behind
	c. Light brown and yellow, nonmetallic
	also: Basal antenodal cells of wings marked with brown; total length < 63 mm
1b	a. Nodus of forewing distinctly beyond middle of wing	Macromia, 2
	b. Vertex bilobed, larger than occiput, which lacks a bulbous swelling behind
	c. Dark, with metallic lustre and bright yellow markings
2a(1b)	a. Males with apex of posterior hamule markedly protuberant beyond the subapical hook	Macromia illinoiensis Walsh
	b. Females with lobes of the subgenital plate convex or obtusely angled apically
	c. Females with tibiae usually 12 mm or shorter
2b	a. Males with apex of posterior hamule not markedly protuberant beyond the subapical hook, smoothly tapered to a short rounded tip	3
	b. Females with lobes of subgenital plate truncate apically
	c. Females with tibiae usually 13 mm or longer
3a(2b)	a. Mesepisternal pale stripes usually well-developed	Macromia taeniolata Rambur
	b. Ventral yellow markings usually absent, or very obscure on Ab7-9
	c. Hindwings commonly > 50 mm
	d. Males with cerci as long as, or slightly longer than, the epiproct, about 5x as long as width at its midlength
	e. Females with lobes of vulvar lamina not contiguous basally
3b	a. Mesepisternal pale stripes often vestigial or absent	Macromia alleghaniensis Williamson
	b. Ventral yellow markings usually readily apparent on Ab7-9
	c. Hindwings usually < 50 mm
	d. Males with cerci slightly shorter than epiproct, about 4x as long as width at midlength
	e. Females with lobes of vulvar lamina contiguous basally

Mature Nymphs

1a	a. Lateral spines of Ab9 extend posteriorly level to tips of cerci	Didymops transversa (Say)
	b. Ab10 without small middorsal hook or carina
	c. Width of head behind eyes roughly equal to that across eyes
	d. Lateral setae 5, premental setae 5 + 1-2
1b	a. Lateral spines of Ab9 not reaching posteriorly level to tips of cerci	Macromia, 2
	b. Ab10 with a small middorsal hook or carina
	c. Width of head narrows posteriorly behind eyes
	d. Premental setae 6, premental setae 5-6 + 3-4
2a(1b)	a. Dorsal hook of Ab6, in lateral view, gently curved and very slender, W:H ratio 0.36-0.52	Macromia alleghaniensis Williamson
	b. Occiput with 3-5 long pale setae (> 2 mm long) medial to compound eye and at middorsum
	c. Dorsum of pterothorax with 6-10 very long setae (> 2 mm) near wing sheath bases
2b	a. Dorsal hook of Ab6, in lateral view, more abruptly and not very slender, W:H ratio ≥ 0.55	3
	b. Occiput with only 1 pale setae at middorsum
	c. Dorsum of pterothorax with fewer, shorter setae (< 1.5 mm) near wing sheath bases
3a(2b)	a. Ratio of S9 posterolateral spine basal W:L 0.8-0.9	Macromia taeniolata Rambur
	b. Metathoracic femur at least 12 mm long (mature nymph)
	c. Ratio of prementum maximum width:head width 0.91-1.20
	d. Apex of S6 middorsal hook projecting posteriorly over anterior portion of S7 (best seen in lateral view)
	also: Uncommon in rivers in southern Michigan
3b	a. Ratio of S9 posterlateral spine basal W:L 0.5-0.6	Macromia illinoiensis Walsh
	b. Metathoracic femur < 12 mm long (mature nymph)
	c. Ratio of prementum maximum width:head width 0.84-0.92
	d. Apex of S6 middorsal hook projecting less posteriorly, does not extend over anterior portion of S7
	also: Widespread throughout state in lakes and rivers

References

Needham JG, Westfall MJ, May ML. 2014. Dragonflies of North America. The Odonata (Anisoptera) Fauna of Canada, the Continental United States, Northern Mexico and the Greater Antilles. Third Edition. Scientific Publishers, Gainesville, Florida, USA. Life histories of some Kansas "backswimmers". Annals of the Entomological Society of America 19:93-101. xiii +658 p.
Tennessen KJ. 2019. Dragonfly nymphs of North America: An Identification Guide. Springer International Publishing, Cham, Switzerland: xiv + 620 p.

Page created: June 10, 2003; Last edited: April 19, 2020 (EB)