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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- Aquatic Insects of Michigan
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 | Thremmatidae |
| 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 | Thremmatidae |
| 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 shell |
||
| 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 | Thremmatidae |
| 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)