Aquatic Insects of Michigan

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

Hydropsychidae and Arctopsychidae of Michigan - Identification

Introduction

[under construction] Some publications (e.g., Morse and Holzenthal 1996) treat Arctopsychidae as a subfamily of Hydropsychidae (as Arctopsychinae), so I treat these two subfamilies together on the same page.

Adults
(adapted from Nimmo 1987, Schmidt 1998)

1a	a. Antennae thick	Arctopsychidae, 2
	b. Both pairs of wings similar in shape and width
	c. Postcostal cell of frontwing short and wide
1b	a. Antennae thin	Hydropsychidae, 3
	b. Hindwing wider than frontwing, and differently shaped
	c. Postcostal cell of frontwing long, usually narrow
2a(1a)	a. Eyes bare	Arctopsyche ladogensis (Kolenati)
	b. Male genitalia prominent and not invaginated within preceding segment
	c. Middle legs of female flattened
2a	a. Eyes hairy	Parapsyche apicalis (Banks)
	b. male genitalia only sightly prominent and invaginated within preceding segment
	c. Middle legs of female not flattened
3a(1b)	a. Discoidal and median cells in front wings small	Macronematinae, Macrostemum zebratum Hagen
	b. Antennae very long and thin
	also: Discoidal cell in hind wings open; forewing brown with strong yellow stripes
3b	a. Sterna of Ab5 with a long filament	Diplectroninae, Diplectrona modesta Banks
	b. Antennae slightly crenate
	also: Hindwing large, rounded, with Sc and R1 markedly bowed distally
3c	a. Sterna of Ab5 at most with a lobe or faint prominence	Hydropsychinae, 4
	b. Antennae slender, cylindrical, not as in 3a or 3b above
	also: Hindwing constricted somewhat distally
4a(3c)	a. Stems of hindwing M and Cu1 not parallel, not close	Cheumatopsyche Wallengren
	b. FI absent
4b	a. Stems of hindwing M and Cu1 parallel, very close together	5
	b. FI present
5a(4b)	a. Forewing crossveins M3+4-Cu1 and Cu1-Cu2 close	Potamyia flava (Hagen)
	b. A in contact with Cu2 prior to wing margin
	c. Hindwing median cell open
5b	a. Forewing crossveins M3+4-Cu1 and Cu1-Cu2 clearly separated	6
	b. A terminated at wing margin
	c. Hindwing median cell closed
6a(5b)	a. Forewing with Cu2 and A meeting at or before the wing margin	Hydropsyche Pictet
	b. Males with phallotremal sclerites enclosed in a mesal cavity
6b	a. Forewing with Cu2 and A ending separately (but very close) on wing margin	Ceratopsyche Ross and Unzicker
	b. Males with phallotremal sclerites exposed, situated dorsally

Larvae (adapted from Morse and Holzenthal 1996)

1a	Genae of head capsule completely separated by single ventral apotome	Arctopsychidae, 2
1b	Genae of head capsule touching ventrally, separating ventral apotome into an anterior and posterior parts, or posterior part inconspicuous	Hydropsychidae, 3
2a(1a)	a. Most abdominal segments with a single long setae in sa2 and sa3 positions, frequently with 1 or 2 shorter setae, but not a tuft	Arctopsyche ladogensis (Kolenati)
	b. Ventral apotome narrowed posteriorly
2b	a. Most abdominal segments dorsally with a tuft of long setae and/or scale hairs on sa2 and sa3 positions	Parapsyche apicalis (Banks)
	b. Ventral apotome of head usually nearly rectangular
3a(1b)	Posterior ventral apotome at least 1/2x as long as median ecdysial line where the genae touch	Diplectroninae, Diplectrona modesta Banks
	also: Meso- and metanotum with transverse furrow
3b	Posterior ventral apotome much less than 1/2x as long as median ecdysial line where the genae touch	4
4a(3b)	a. Abdominal gills with up to 40 filaments arising fairly uniformly along central stalk	Macronematinae, Macrostemum zebratum Hagen
	b. Fore trochantin never forked
	also: Tibia and tarsus of each prothoracic leg with dense, dorsal setal fringe; dorsum of head flattened and margined with a sharp carina
4b	a. Abdominal gills with up to 10 filaments arising mostly near the apex of the central stalk	Hydropsychinae, 5
	b. Fore trochantin usually forked
5a(4b)	a. Prosternum with a pair of large sclerites in the intersegmental fold posterior to prosternal plate	6
	b. Frontoclypeus entire
5b	a. Prosternum with a pair of usually small sclerites posterior to prosternal plate	7
	b. If sclerites large, frontoclypeus with shallow mesal excision
6a(5b)	a. Dorsum of abdomen with numerous plain hairs in addition to minutes pines on at least the first 3 abdominal segments, and scale hairs present on at least the last 3 segments	Hydropsyche Pictet
	b. Club hairs absent
6b	a. Dorsum of abdomen with plain hairs and club hairs only	Ceratopsyche Ross
	b. Minute spines and scale hairs absent
7a(5b)	a. Anterior ventral apotome of head with a prominent anteromedian projection	Potamyia flava (Hagen)
	b. Posterior margin of each sclerite on Ab9 sternum entire
	c. Lateral border of each mandible flanged
	d. Fore trochantin not forked
7b	a. Anterior ventral apotome of head without a prominent anteromedian projection	Cheumatopsyche Wallengren
	b. Posterior margin of each sclerite on sternum of Ab9 emarginated
	c. Mandibles not flanged
	d. Fore trochantin forked

References

Moulton SR, Stewart KW. 1996. Caddisflies (Trichoptera) of the interior highlands of North America. The American Entomological Institute, Volume 56. iii + 313 p.
Nimmo AP. 1987. The adult Arctopsychidae and Hydropsychidae of Canada and adjacent United States. Questiones Entomologicae 23:1-189.
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.
Morse JC, Holzenthal RW. 1996. Trichoptera genera, pp. 350-386 in Merritt RW, Cummins KW, An Introduction to the Aquatic Insects of North America, 3rd Edition. Kendall/Hunt Publishing Company, Dubuque, Iowa. xiii + 862 p.

Page created: June 18, 2003; Last edited: November 07, 2013 (EB)