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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Trichoptera (Caddisflies) of Michigan - Identification

Introduction

This provisional is key based on the literature cited below, and also serves as links for keys to some trichopteran keys for some families as indicated by links within the key or in the navigation frame to the left.

Adults
(adapted from Wiggins 1996, Schmid 1998)

    1a a. Very small (length 1-5 mm) and very hairy species with both pairs of wings very narrow, tapered often with very long fringes, especially in hind wings (fringe length about the width of the hindwing) Hydroptilidae
    b. Mesoscutum lacking setal warts, mesoscutellar setal warts transverse and meeting mesally to form an angulate ridge
    c. Front tibia never with more than single spur
    d. Lateral ocelli close to eye margin or absent
    1b Species without the above combination of characters 2
    2a(1b)

    Ocelli present

    3
    2b Ocelli absent 10
    3a(2a) a. M of hind wings simple, or if 2-branched, then each banch distinct from base, or discoidal cell open at base, RS double, beginning at the base of wing Uenoidae
    b. Anterior edge of hind wing with row of stout, hooked setae
    3b M of hind wings 2-branched or 3-branched 4
    4a(3b) A of front wings composed of 3 veins reaching the edge of the wing independently Goeridae, Goera (in part)
    4b A of front wings with 3 confluent branches that form 2 or 3 closed cells 5
    5a(4b) Maxillary palpi 3-segmented
    Limnephilidae, Apataniidae, males
    5b Maxillary palpi 4-segmented Phryganeidae, males
    5c Maxillary palpi 5-segmented 6
    6a(5c) Terminal maxillary palp (segment 5) flexible, usually at least twice as long as preceding segment Philopotamidae
    6b Terminal maxillary palp similar to others in structure, usually about same length as preceding segment 7
    7a(6b) a. Maxillary palp with segments 1-2 very short and equal in length, segment 5 ending in a point Rhyacophilidae, Rhyacophila
    b. Discoidal cell in both pairs of wings open
    c. Spurs 3,4,4, fore tibia with a preapical spur
    7b a. Maxillary palp with segments 1 and 2 subglobular, equal or not equal in length but with segment 5 not ending in a point 8
    b. Discoidal cell in front wings closed
    c. Spurs 2,4,4 or 0,4,4 or 2,4,4, fore tibia lacking a preapical spur
    8a(7b) a. Segment 2 of maxillary palpi equal or subequal Glossosomatidae
    also: Posterior cephalic setal warts oval or round, and widely separated on meson; pronotum with a mesal pair of warts that are well separated
    8b a. Segment 2 of maxillary palpi clearly longer than segment 1 9
    also: Discoidal cell on both wings closed
    9a(8b) Front tibia with 2 or more spurs, middle tibia with 2 preapical spurs, spurs usually 2,4,4 Phryganeidae
    9b Front tibia with a single spur, middle tibia with 0 or 1 preapical spurs, spurs usually 1,2-3,4 Limnephilidae, Apataniidae
    10a(2b) Segment 5 of maxillary palp flagellate, long, flexible (usually) with numerous cross-striae, and different in structure from, and generally much longer than, the preceding segments 11
    10b Segment 5 of maxillary palp not flagellate, similar to the others segments in structure, and usually approximately the same length as preceding segment (segment 4) 14
    11a(10a) a. Long discoidal cell in front wings Polycentropodidae
    b. Median cell open or closed, beginning apical to the proximal tip of the discoidal cell (fork has a stem)
    c. Maxillary palp segment 3 inserted before apex of segment 2, which is spinose
    also: Foretibia with a preapical spur, or if spur absent (Cernotina), length of basal segment of tarsus less than twice the length of the longer apical spur
    11b a. Short discoidal cell in front wings 12
    b. Median cell closed and beginning basal to proximal tip of discoidal cell (fork has no stem)
    c. Maxillary palp segment 3 inserted at apex of segment 2
    12a(11b) a. Spurs 3,4,4 Dipseudopsidae, Phylocentropus
    b. Antennae of male longer than front wings
    12b a. Spurs 2,4,4 13
    b. Antennae of male shorter than front wings
    13a(12b) a. Thyridial cell on front wings very small, located at the base of the wing, and without contact with the median cell Psychomyiidae
    b. Hing wings narrower than front wings
    c. F1 absent, with discoidal cell open and the anal area reduced
    13b a. Thyridial cell on front wings large, medianly positioned and in contact with the median cell Hydropsychidae, Arctopsychidae
    b. Hing wings equal in width or wider than the front wings
    c. F1 almost always present, discoidal cell closed and the anal area well developed
    14a(10b) Discoidal and thyridial cells of front wings absent also: Antennae little, if any, longer than body; middle tibia with 2 preapical spurs Molannidae, Molanna
    14b Discoidal and thyridial cells of front wings present 15
    15a(14b) Middle tibia without preapical spurs, but with black spines 16
    15b Middle tibiae with preapical spurs, and with or without black spines 20
    16a(15a) a. Antennae very thin, longer than front wings and much longer than body
    Leptoceridae
    b. Very long, slender maxillary palpi clothed with dense, erect hairs
    c. Pronotum partially concealed under the mesonotum also: Middle tibia lacking preapical spurs
    16b a. Antennae shorter than front wings 17
    b. Maxillary palpi thicker than above
    c. Pronotum clearly visible from above
    17a(16b) a. Hind wings with basal half of costal margin equipped with hooks and forming a broad costal angle Helicopsychidae, Helicopsyche borealis(Hagen)
    b. Dorsum of head with posterior setal warts very large, extending from mesal margin of eye to mid-dorsal line and anteriorly to middle of head
    17b a. Hind wings without hooks or costal angel 18
    b. Dorsum of head with posterior setal warts relatively smaller than above, or antennae 1.5x longer than forewing
    18a(17b) a.Front wings with crossvein between R1 and R2 Sericostomatidae
    b. F-1 merges with discoidal cell for a long distance and the Cu2 ends on Cu1b
    18b a. Front wings without a crossvein between R1 and R2+3 Brachycentridae (in part)
    b.F-1 merges with discoidal cell for a short distance, the Cu2 and Cu1b joined by crossveins
    19a(15b) Median cell of crossvein closed, and antenna much longer than the front wings Calamoceratidae (eastern, not known in or near Michigan)
    19b Median cell of front wings open or absent, antennae shorter than the front wings Odontoceridae
    19c Median cell of front wings open or absent b. Antennae shorter than front wings 20
    20a(19c) Thyridial or subthyridial cell of front wings broadened at the apex Goeridae, Goera (in part)
    20b Thyridial or subthyridial cell of front wings not broadened at the apex 22
    21a(20b) a. Spruts 2,4,4 and hairy
    Lepidostomatidae
    b. Middle tibia without black spines
    20b a. Spurs 2,3,3 or 2,4,4, and not hairy Brachycentridae (in part)
    b. Middle tibia with black spines

Pupae (modified from Ross 1944 and Wiggins 1996)

    1a

    Two pairs of hook plates present on Ab3-5

    2
    1b Two pairs of hook plates never present together on each of segments Ab3-5 3
    2a(1a) Very small, < 6 mm also: apex of abdomen membranous, without definite lobes except ventral membranous ones which contain developing genitalic parts; mandibles without teeth or serrations Hydroptilidae
    2b Larger, > 6 mm 11
    3a(1b) Abdomen lacking lateral fringe, although isolated setal tufts sometimes present
    4
    3b Abdomen with lateral fringe, the fringe continuous where present 14
    4a(3a)

    Mandibles with only a single apical point, althought his is sometimes extended as a slender filament

    5
    4b Mandibles with a least one subapical toothlike point more prominent than the others in addition to an apical point 11
    5a(4a) Hook plates on Ab7, frequently also on Ab8 6
    5b Hook plates not extending posteriorly beyond Ab6 10
    6a(5a) Hook plate Vp with 6 or more hooks
    7
    6b Hook plate Vp with only 2 or 3 hooks 18
    7a(6a) Hook plates present on Ab2 also: Hooks of plates on Ab2-4 arranged in an arc curved concavely anteriorly
    Psychomyiidae
    7b Hook plates absent from Ab2 8
    8a(7b) Anal processes very slender and pointed, frequently hooked apically, Ab8 lacking hook plates Uenoidae
    8b Anal processes rounded lobes, pair of hook plates usually present on Ab8 9
    9a(8b) Terminal segment of abdomen with 4 bushy processes, 2 apical and 2 basolateral
    Dipseudopsidae, Phylocentropus
    9b Terminal segment with only 2 apical bushy processes Polycentropodidae
    10a(5b) Antennae little, if any, longer than the body, not coiled around anal processes also: Anal processes simple lobes closely appressed along midline, with stout apical bristles longer than processes themselves
    Helicopsychidae, Helicopsyche borealis(Hagen)
    10b Antennae much longer than the body, coiled around anal processes 23
    11a(2b, 4b) Abdominal gills present, 2 pairs of hook plates present on Ab3 Hydropsychidae, Arctopsychidae
    11b Abdominal gills absent, 1 or 2 pairs of hook plates on Ab3 12
    12a(11b) One pair of hook plates on Ab4 Philopotamidae
    12b Two paris of hook plates on Ab4 13
    13(12b)

    Ab8 and/or Ab9 with a pair of small hook plates, and/or 2 patches of long setae at apex of abdomen

    Glossosomatidae
    13b Ab8 and 9 lacking hook plates; also: apex of abdoemn lacking patches of setae Rhyacophilidae
    14a(3b) Lateral fringe of abdomen extending anteriorly from Ab7 or Ab8 to Ab5 or Ab6
    15
    14b Lateral fringe of abdomen extending anteriorly from Ab7 or Ab8 to Ab3 or Ab4 21
    15a(14a) Anal processes short or lobate, < 5x longer than wide
    16
    15b Anal processes long and slender, > 5x longer than wide 17
    16a(15a) Anterior hook plates longer than wide, or both dimensions approximately the same, and most plates with 2-4 hooks 18
    16b Anterior hook plates wider than long, and usually each with 5 or more hooks 22
    17a(15b, 16a) Anterior hook plates wider than long
    Brachycentridae
    17b Anterior hook plates longer than wide, or the two dimensions approximately equal 18
    18a(6b, 16b, 17b) Bristles of labrum usually hooked apically, antenae usually with dorsal tuft of hairs
    19
    18b Bristles of labrum never hooked apically, antennae usually with ventrolateral tuft of hairs 20
    19a(18a) a. Anal processes extremely slender at the apex, threadlike and sinuate
    Goeridae, Goera
    b. No apical setae on apical processes
    19b a. Anal processes not greatly narrowed at the apex, and not sinuate Limnephilidae, Apataniidae
    b. Apex of anal processes usually 2-3 apical hairs
    20a(18b)

    Mesal margin of mandible concave in outline, apex pointed; anterior hook plates with 2 or 3 hooks

    Sericostomatidae, Agarodes
    20b Mesal margin of mandible straight in outline, apex usually attenuate; most anterior hook plates with 1 hook Odontoceridae
    21a(14b) Anal processes short and quadrate, or triangular in dorsal aspect
    22
    21b Anal processes long and slender 23
    22a(16b, 21a) a. Ab1 with dorso mesal spined lobe
    Phryganeidae
    b. Anal processes in dorsal aspect short and roughly quadrate
    22b a. Ab1 lacking dorsomesal spined lobe Lepidostomatidae, Lepidostoma
    b. Anal processes more elongate than above in dorsal aspect and roughly triangular
    23a(10b, 21b) a. Anal processes with apical bristles approximately 1/2x long as processes themselves
    Molannidae, Molanna
    b. Antennae little longer than body, and not coiled apically
    23b a. Anal processes with much shorter apical bristles, or with none Leptoceridae
    b. Antennae much longer than body and coiled around base of anal processes

Larvae (adapted from Wiggins 1996a, b)

    1a a. Anal claw comb-shaped
    Helicopsychidae, Helicopsyche borealis (Hagen)
    b. Portable case of sand grains resembling a snail shellHelicopsyche borealis and case
    1b a. Anal claw hook-shaped 2
    b. Case not resembling a snail shell, or larvae do not construct a case
    2a(1b) Dorsum of all three thoracic segment largely covered by sclerites 3
    2b First two (pro- and mesonotum) thoracic segments covered by sclerites, metanotum membranous (note: one genus (Ceraclea) of Leptoceridae have lightly pigmented mesonotal sclerites, but with dark curved lines on posterior half) 4
    2c Only the prontoum covered by sclerites, meso- and metanotum membranous 13
    3a(2a) a. Abdomen with ventrolateral rows of branched gills Hydropsychidae, Arctopsychidae
    b. Anal prolegs, which project freely from the abdomen, with a bursh of many long hairs at the base of the large anal claw
    c. Posterior margin of meso- and metanotal plates lobate
    d. Larvae construct fixed retreats of detritus and rock fragments
    3b a. Abdomen without ventrolateral rows of branched gills Hydroptilidae
    b. Anal proleg, which does not usually project freely from the abdomen, without a brush of setae, and anal claw very small
    c. Posterior margin of meso- and metanotal plates straight
    d. First three instars free-living, fourth instar larvae construct purse- or barrel-shaped portable cases, or flat silken domes fastened to rocks
    4a(2b) Antennae clong and prominent, at least 6x long as wide, and/or mesonotal sclerotized plates lightly pigmented except for a pair of dark curved lines on the posterior half Leptoceridae
    4b Antennae much shorter, < 3x long as wide, or not apparent, and mesonotum never with a pair of dark curved lines as above 5
    5a(4b) Metatarsal claw modified to form a short, setose stub Molannidae, Molanna
    also: Larvae construct portable cases of sand grains with lateral flanges
    5b Metatarsal claw structure not different from those of the other legs 6
    6a(5b) a. Ab1 lacking both dorsal and lateral humps Brachycentridae
    b. Each metanotal sa1 usually lacking entirely or, if represented only by a single seta without a sclerite
    c. Mesonotal sclerites subdivided
    d. Pronotum divided by a sharp furrow across the middle, area anterior to furrow depressed
    6b a. Ab1 with at least a lateral hump that may not be apparent, dorsal hump present or absent 7
    b. Metanotal sa1 always present, represented by a sclerite bearing at least one (usually more) seta
    7a(6b) Labrum with a transverse row of approximately 16 long setae across the central part
    Calamoceratidae (not in Michigan)
    b. Larvae construct case of a hollowed twig, or of leaves and bark variously arranged
    7b Labrum with no more than 6 long setae across the central part 8
    8a(7b) a. Antennae situated at or very close to the anterior margin of the head capsule 9
    b. Prosternal horm absent
    c. Larvae construct cases usually of rock fragments
    8b a. Antennae removed from the anterior margin of the head capsule and approaching the eye 10
    b. prosternal horn present, although sometimes short
    c. Larvae construct cases of rock fragments or plant materials
    9a(8a) a. Anal proleg with a dorsal cluster of approximately 30 or more setae posteomesad of the lateral sclerite Sericostomatidae
    b. Fore trochantin relatively large, the apex hook-shaped
    c. Larvae construct cases mainly of sand
    9b a. Anal proleg with no more than 3-5 dorsal setae posteromesad of lateral sclerite, sometimes short spines Odontoceridae
    b. Fore trochantin small, the apex not hook-shaped
    c. Larval case mainly of small rock fragments difficult to crush
    10a(8b) a. Antennae situated close to the anterior margin of the eye
    Lepidostomatidae, Lepidostoma
    b. Ab1 without a median dorsal hump
    c. Larvae construct several types of cases, frequently 4-sided
    10b a. Antennae situated approximately halfway between the eye and the anterior margin of the head capsule 11
    b. Ab1 almost always with a median dorsal hump
    11a(10b) a. Mesopleuron modified, usually extended anteriorly as a prominent process Goeridae, Goera
    also: Mesopleuron occasionally only spinose; Larvae construct small tubular cases with pepples along the side (ballast stones)
    11b a. Mesopleuron, unmodified, not extended as an actue prominent process 12
    12a(11b) Mesonotum with the anteromesal border emarginate, the two primary sclerites closely aligned on the mid-dorsal line Uenoidae
    also: Larvae construct cases with (ballast) stones arranged linearly along each side
    12b Mesonotum with the anteromesal border not emarginate, though occasionally the two primary sclerites are widely separated on the mid-dorsal line Limnephilidae, Apataniidae
    13a(2c) Ab9 with a dorsal sclerite 14
    13b Ab9 without a dorsal sclerite 16
    14a(13a) a. Metanotal sa3 usually consisting of a cluster of setae arising from a small rounded or ovoid sclerite Phryganeidae
    b. Prosternal horn present
    c. Larvae construct tubular portable cases, usually of plant materials
    14b a. Metanotal sa3 consisting of a single seta without a sclerite 15
    b. Prosternal horn absent
    c. Larvae construct cases tortoise-like case of rock fragments, or without a case
    15a(14b) a. Basal half of anal proleg broadly joined with Ab9 Glossosomatidae
    b. Anal claw with at least one dorsal accessory hook
    c. Larvae construct tortoise-like portable cases of rock fragments
    15b a. Most of anal proleg free from Ab9 Rhyacophilidae, Rhyacophila
    b. Anal claw without dorsal accessory hooks, although a secondary lateral claw may be present
    c. Larvae free-living without portable cases, but construct pupal enclosures
    also: Protrochantin conspicuous
    16a(13b) a. Labrum membranous and T-shaped, which often withdraws from view in preserved specimens Philopotamidae
    b. Larvae construct fixed sac-shaped nets of silk, principally lotic
    16b Labrum sclerotized, rounded and articulated in normal way 17
    17a(16b) a. Trochantin of prothoracic leg broad, hatchet-shaped, separated from episternum by a dark suture line
    Psychomyiidae
    b. Larvae construct fixed tubular retreats on rocks and logs
    17b a. Trochantin of prothoracic leg with an acute (pointed) apex, fused completely with the episternum without a separating suture 18
    18a(17b) a. Tarsi of all legs strongly flattened, tibiae shorter than tarsi Dipseudopsidae, Phylocentropus
    b. Larvae burrow in sandy deposits and construct tubes of sand grains or flattened retreats
    18b a. Tarsi of all legs normal, not flattened, tibiae longer than tarsi Polycentropodidae
    b.Larvae construct exposed funnel-shaped capture nets or flattened retreats

References

    Ross HH. 1944. The Caddis Flies, or Trichoptera, of Illinois. Bulletin of the Illinois Natural History Survey 23(1):1-326.
    Schmid F. 1998. The Insects and Arachnids of Canada. Part 7. Genera of the Trichoptera of Canada and Adjoining or Adjacent United States. NRC Research press, Ottawa, Ontario, Canada. 319 pp.
    Wiggins GB. 1996a. Trichoptera families, pp. 309-349 in: Merritt RW, Cummins KW, An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company, Dubuque, Iowa. 862 + xiii.
    Wiggins GB. 1996b. Larvae of the North American caddisfly genera (Trichoptera). University of Toronto Press, Toronto, Ontario. 457 + xiii.

Page created: May 17, 2003; Last edited: November 07, 2013 (EB)