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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under construction

Adults (adapted from Wiggins 1998)

    1a a. Forewings yellow with dark brown reticulations
    Oligostomis ocelligera (Walker)
    b. Hind wings largely uniform dark brown except for yellow band that curves to follow the posterior margin
    1b a. Forewings not colored as above 2
    2a(1b) a. Maxillary palpi with four segments
    Males, 3
    b. External genitalia with paired, articulated appendages
    2b a. Maxillary palpi with five segments Females, 9
    b. External genitalia lacking paired, articulated appendages
    3a(2a) Ab9 sternum with posteroventral margin flattened, with concavity or with sclerotized points or ridges
    3b Ab9 sternum with posteroventral margin simple in outline, sometimes scoop-like but lacking structures as above 6
    4a(3a) Ab9 sternum extended beneath the bases of the inferior appendages as a broad ledge with a caudal concavity bordered by stout teeth
    4b Ab9 sternum not extended as a broad ledge beneath the bases of the inferior appendages, and marginal teeth lacking 5
    5a(4b) Ab9 sternum with an invaginated pocket bordered by raised, roughened margins
    Hagenella canadensis (Banks)
    5b Ab9 sternum with a short, horizontal ledge between the inferior appendages Beothukus complicatus (Banks)
    6a(3b) a. Ab10 with an enlarged basal process extending posteriorly to apex of the inferior appendages or beyond, with a cluster of stout, spine-like seate or points at the apex
    b. Phallotheca short, itx apex extended ventrally into two sclerotized prongs or dentate processes
    c. Length of fore wing 17-25 mm
    6b a. Ab10 lacking enlarged processes and clusters of stout, spine-like seate as above 7
    b. Length of fore wing variable, 9-26 mm
    7a(6b) a. Inferior appendages with adjacent ventromesal edges enlarged, meeting on the median line, sometimes apparently fused, and in some species with sclerotized points Banksiola
    also: Inferior appendages with a slender terminal segment continuously sclerotized dorsolaterally but connected mesally by a membranous area bearing a small, dark sclerite
    7b a. Inferior appendages with adjacent mesal edges not greatly enlarged, and not meeting along the median line 8
    also: Phallotheca an elongate,l sclerotized tub
    8a(7b) Phallotheca with a pair of stout, hook-like endothecal spines arising from the ventral surface near apex
    Fabria inornata (Banks)
    8b Phallotheca either lacking endothecal spines, or if two or more spines are present, these are straight and slender, not hook-like Agrypnia

    9a(2b) In ventral view, subgenital plate narrowed towards the apex 10
    9b In ventral view, subgenital plate not narrowed towards apex, rather its posterior margin broad and more or less truncate 12
    10a(9a) Apex of the subgenital plate with a single median ovoid lobe, or a pair of flap-like lobes Agrypnia
    10b Apex of the subgenital plate with 2-3 processes, in some species somewhat blade-like in appearance 11
    11a(10b) a. Ab10 with prominent thumb-like lateral lobes Beothukus complicatus (Banks)
    b. Fore wing length about 12 mm
    11b a. Ab10 lacking lateral lobes Phryganea
    b. Larger insects, fore wing length 22-29 mm
    12a(9b) Posterior margin of the subgenital plate broadly rounded, and without lobes or processes Fabria inornata (Banks)
    12b Posterior margin of the subgenital plate extended into apical lobes or processes 13
    13a(12b) a. Subgenital plate terminated into lobes and processes of different types, but not as small, triangular-shaped median lobe Banksiola
    also: Posterior margin of the subgenital plate with with processes and lobes usually arranged in groups of three or four
    13b Subgenital plate terminated into a small, median lobe, usually triangular in shape, with a slender, finger-like process on each side 14
    14a(13b) Opening to the genital passage overhung by a sclerotized, hood-like structure Hagenella canadensis (Banks)
    14b Opening to the genital passage not overhung by a sclerotized, hook-like structure Ptilostomis

Pupae (adapted from Wiggins 1998)

    1a Pupa decticous, mandibles with sclerotized blades pointed 2
    1b Pupa adecticous, mandibles reduced to short, membranous lobes that lack blades 4
    2a(1a) In dorsal view, dorsomedian process of Ab1 long, extended well beyond the mid-point of Ab2, with its apex deeply notched Fabria inornata (Banks)
    2b In dorsal view, dorsomedian process of Ab1 usually shorter, not extended beyond the mid-point of Ab2, and its apex less deeply notched 3
    3a(2b) a. Mandibular blade extended at an abrupt angle from the base Phryganea
    also: Dorsal hook-plates present on Ab4-7; Ab9 with two angular dorsal lobes, each bearing seta, just anterad of the anal processes
    3b a. Mandibular blade evenly curved from the base to apex Agrypnia
    also: Mandibles pointed and longer than labrum, blade substantially longer than its base, the two delimited by a mesal constriction
    4a(1b) Front of head in lateral and dorsal aspects extended prominently Hagenella canadensis (Banks)
    also: Anal processes evenly rounded, not emarginate
    4b Front of head rounded between the eyes, but not prominently extended as above 5
    5a(4b) Labrum narrow, its basal half constricted
    Beothukus complicatus (Banks)
    5b Labrum wider, its basal half not constricted 6
    6a(5b) Anal processes flattened but scarely concave dorsally
    Oligostomis ocelligera (Walker)
    6b Anal processes flattened and strongly concave dorsally 7

    Anal processes short, rounded to truncate in lateral aspect

    7b Anal processes longer, tapered in lateral aspect Banksiola

Larvae (adapted from Wiggins 1998)

    1a a. Mesonotum with prominent sclerites at the sa1 positions, which are clearly separated by a membranous median area 2
    b. Larval case of ring construction
    1b a. Mesonotum lacking sclerites at the sa1 positions 3
    b. Larval case of spiral or ring construction
    2a(1a) Antennae long, approximately equal in length to the diameter of the cluster of pigmented stemmata Beothukus complicatus (Banks)
    2b Antennae shorter than above Oligostomis ocelligera (Walker)
    3a(1b) a. Coxal combs of fore legs well developed, their structure apparent at magnification of approximately 50x 4
    b. Case usually of spiral form, but never ring construction
    3b a. Coxal combs of fore legs small, appearing as tiny raised points at magnifications of approximately 50x 5
    b. Case of spiral or ring construction
    4a(3a) a. No sternellum present between the prothoracic coxae Phryganea
    b. Coxal combs on both pro- and mesothoracic legs large, and with basal axes transverse to the long axis of the coxae
    4b a. Sternellum usually present between prothoracic coxae Agrypnia
    b. Coxal combs on prothoracic legs with the axis of the base transverse to the long axis of the coxa, coxal combs of the mesothoracic legs both transverse and parallel to the long axis of the coxa
    5a(3b) a. Meso- and metanota with a pair of longitudinal, irregular dark bands Banksiola
    b. Case of spiral construction
    5b a. Meso- and metanota mostly uniform in color, without irregular dark bands 6
    b. Case of spiral or ring construction
    6a(5b) a. Head and pronotum uniform light brown, lacking contrasting light and dark markings except for muscle scars

    Hagenella canadensis (Banks)

    b. Case of ring construction
    6b a. Head and pronotum with dark markings contrasting prominently with the light ground color 7
    b. Case of spiral or ring construction
    7a(6b) a. Pronotum with a dark band only along the anterior border Fabria inornata (Banks)
    b. Case basically of spiral construction but with trailing ends that convey a bushy, irregular appearance
    7b a. Pronotum with a transverse dark band on each side, but central in position and not extended to the anterior border Ptilostomis
    b. Case of ring construction


    Wiggins GB. 1998. The caddisfly family Phryganeidae (Trichoptera). University of Toronto Press, Toronto, Canada. xi + 306 p.

Page created: October 14, 2003; Last edited: November 07, 2013 (EB)