Aquatic Insects of Michigan

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

Toggle Menu

Nemouridae (Forestflies) of Michigan - Identification


[under construction]

(adapted from Hitchcock 1974 (Ricker 1952), Stewart and Harper 1996)

    1a Gill remnants on cervix (neck region), each gill composed of 5-18 branches and divided down to base
    Amphinemura Ris, 2
    also: Male paraprocts with 3 lobes, and cerci unmodified; female Ab7 sternum broadly rounded, not covering all of Ab8 sternum
    1b No gill remnants on cervix 5
    2a(1a) a. Epiproct and paraprocts modified Males, 3
    b. Ab8 not modified as a subgenital plate
    2b a. Epiproct and paraprocts unmodified Females, 4
    b. Ab8 modified as a subgenital plate
    3a(2a) Paraprocts short, not recurved onto Ab10 tergite, inner members armed with only 4-6 spines Amphinemura linda (Ricker)
    3b Paraprocts long, recurved over at least part of Ab10 tergite, inner members armed with at least 8 spines and much produced posteriorly at bend, where it is thin and compressed, its tip unsclerotized and not recurved Amphinemura delosa (Ricker)

    Border of subgenital plate with a median notch and small, but with a definite V- or U-shaped lateral notch on either side

    Amphinemura delosa (Ricker)
    4a Border of subgenital plate merely sinuate laterally Amphinemura linda (Ricker)
    5a(1b) Veins A1 and A2 of forewing joined near the margin Soyedina vallicularia (Wu)
    5b Veins A1 and A2 of forewing separate 6
    a. Epiproct and paraprocts modified Males, 7
    b. Ab8 not modified as a subgenital plate
    6b a. Epiproct and paraprocts unmodified Females, 11
    b. Ab8 modified as a subgenital plate

    Cerci sclerotized or enlarged

    7b Cerci membranous, unmodified 9
    also: Ab9 sternum with a vesicle
    8a(7a) Cerci with subterminal spines
    Nemoura trispinosa Claassen
    8b Cerci without spines, but elongated and curved Ostrocerca albidipennis (Walker)
    9a(7b) Ab10 tergum produced into 2 large lobes covering the cerci
    Shipsa rotunda (Claassen)
    9b Ab10 tergum, if produced, not so enlarged Prostoia Ricker, 10
    also: Epiproct long and simple
    10a(9b) Basal processes of epiproct twisted, divergent, and more than half as long as the epiproct
    Prostoia similis (Hagen)
    10b Basal processes of epiproct short (< 1/6x long as epiproct), appressed and easily overlook Prostoia completa (Walker)
    11a(6b) Ab7 sternum large, extending over Ab8 sternum
    Nemoura trispinosa Claassen
    11b Ab7 sternum short or unmodified 12
    12a(11b) Ab8 sternum not extending over Ab9 sternum, and unsclerotized except at margin
    Prostoia Ricker, 13
    also: Wings distinctly banded
    12b Ab8 sternum extending over Ab9 sternum as a distinct subgenital plate 14
    13a(12a) Ab8 sternum distinctly produced laterally, and with a large median notch
    Prostoia similis (Hagen)
    13b Ab8 sternum little, or not at all, produced, and a median notch absent or small Prostoia completa (Walker)
    14a(12a) Ab8 sternum small
    Shipsa rotunda (Claassen)
    14b Ab8 sternum large Ostrocerca albidipennis (Walker)
    also: Ab7 sternum often with a small nipple-like projection

Mature nymphs (adapted from Harper and Hynes 1971, Stewart and Stark 2000)

    1a Gills present in the neck region, in ventral view the four anterior thoracic gills with 5 or more filaments originating near their basal trunks
    Amphinemura Ris, 2
    also: Gill filaments approximately of equal length, emerging equally from base and usually not secondarily branched
    1b Gills absent from neck region 3
    2a(1a) Larger bristles on femora and tibiae the same color as the leg, or only slightly darker
    Amphinemura delosa (Ricker)
    also: Spring species, mature larvae found April-July
    2b Larger bristles on femora and tibiae markedly darker than remainder of leg Amphinemura linda (Ricker)
    also: Autumn species, mature larvae found late July-October
    3a(1b) Pronotum angular at corners and with a definite lateral notch
    Soyedina vallicularia (Wu)
    3b Pronotum with rounded corners and without a lateral notch 4
    4a(3b) a. Pronotum with a distinct single, lateral fringe of bristles that are usually about equal in length, sometimes longer on the corners
    Nemoura trispinosa Claassen
    b. Meso- and metanota and wingpads with a distinct fringe of bristles on the lateral margins
    also: Fore tibia with a combination of numerous bristles and sparse (8-10) fine outer fringe of hairs
    4b a. Pronotum with only tiny bristles (except Ostrocerca) and not arranged as a distinct regular lateral fringe 5
    b. Fore tibia with combinations other than numerous bristles and sparse, fine outer fringe hairs
    5a(4b) a. Fore tibia with two rows of moderately long robust bristles, and a sparse fringe of fine hairs
    Ostrocerca albidipennis (Walker)
    b. Pronotum with short, irregularly-spaced marginal bristles
    5b a. Fore tibia without distinct rows of robust bristles, and the fringe of fine hairs complete 6
    b. Pronotum with tiny, inconspicuous bristles
    also: Middle and apical cercal segments with dorsal or ventral intersegmental hairs or both, some 0.5x or more as long as segments
    6a(5b) a. Tibia with short, stout bristles along their outer margins
    Prostoia Ricker, 7
    b. Pronotum relatively shorter, dorsal width greater than its length
    6b a. Tibia without stout bristles along the outer margins Shipsa rotunda (Claassen)
    b. Pronotum relatively long, length and width about equal
    7a(6b) a. Longest marginal bristles on apical abdominal terga aabout 3/4x as long as the corresponding tergum
    Prostoia completa (Walker)
    b. Intermediate hairs on cercal segments well developed
    c. White spots on head, covering both sides of the Y-ecdysial line
    7b a. Longest marginal bristles on apical abdominal terga shorter, about 1/3x as long as the corresponding tergum Prostoia similis (Hagen)
    b. Intermediate hairs on cercal segments poorly , or not at all, developed
    c. White spots on head restricted to the area posterior to Y-ecdysial line


    Harper PP, Hynes HBN. 1971. The nymphs of the Nemouridae of eastern Canada. Canadian Journal of Zoology 49:941-947.
    Hitchcock SW. 1974. Guide to the Insects of Connecticut. Part VII. The Plecoptera or stoneflies of Connecticut. State Geological and Natural History Survey of Connecticut Bulletin 107:1-262.
    Ricker W. 1952. Systematic studies in Plecoptera. Indiana University Publication Science Series 18:1-200.
    Stewart KW, Harper PP. 1996. Plecoptera, pp. 217-266 in Merritt RW, Cummins KW (eds.). An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company: Dubuque, Iowa.
    Stewart KW, Stark BP. 2002. Nymphs of North American stonefly genera. Second Edition. The Caddis Press: Columbus, Ohio. xii + 510 p.

Page created: November 30, 2003; Last edited: November 07, 2013 (EB)