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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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)

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, its width at half height less than half its height Macromia alleghaniensis Williamson
    b. Frontal horn relatively erect, distally directed upward at more than a 45° to plane of vertex between the eyes
    2b a. Dorsal hook of Ab6, in lateral view, more abruptly and not very slender, its width at half height greater than half its height 3
    b. Frontal horn projecting anteriodorsally, distally directed upward at about 45° to plane of vertex between the eyes
     
    3a(2b) a. Nymphs large, total length > 31 mm Macromia taeniolata Rambur
    b. Mid-dorsal hook on Ab6 stout, its width-to-height ratio greater than 0.80
    c. Height of mid-dorsal hook on Ab2 usually shorter (< 0.85x) than that on Ab3
    d. Frontal horn blunt
    also: Rivers in southern Michigan
    3b a. Nymphs smaller than above, total length < 30 mm Macromia illinoiensis Walsh
    b. Mid-dorsal hook on Ab6 more slender than above, its width-to-height ratio less than 0.65 (0.62-0.64)
    c. Height of mid-dorsal hook on Ab2 nearly (> 0.9x) as high as that on Ab3
    d. Frontal horn sharp
    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.

Page created: June 10, 2003; Last edited: July 3, 2016 (EB)