Aquatic Insects of Michigan

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

Perlodidae (Springflies (Perlodinae) and Stripetails (Isoperlinae) of Michigan - Identification

Introduction

Perlodids are generally medium to large stoneflies, principally predaceous as nymph, and are common in cool to cold streams and sometimes in wind-swept portions of clean lakes. A number of species of Isoperla tend to be smaller, and univoltine, whereas larger species in Michigan are semi-voltine, especially towards the north. Isoperla and Isogenoides are particularly common in Michigan trout streams in the northern Lower Peninsula and the Upper Peninsula.

Adults
(adapted from Kondratieff 2004, Stewart and Harper 1996)

1a	a. Male Ab10 tergum usually deeply cleft, when entire, paraprocts extended as long, erect half cyliners	Perlodinae, 2
	b. Often with gill remnants on submentum, cervix, or thorax
	c. Arms of mesoscutal ridge leading to the front end, or hind end, of furcal pits, or absent
	d. Sometimes with supplementary crossveins in R1-Rs space
	e. Pronotum with a narrow, median, light stripe, the margins of the prontal disk usually dark
1b	a. Male Ab10 tergum entire, or cleft shallow or narrow, and paraprocts unmodified or transformed into a recurved hooks or knobs	Isoperlinae, 10
	b. No gill remnants
	c. Arms of mesoscutal ridge leading to the hind end of furcal pits
	d. No supplementary veins in R1-Rs space, though rarely in Rs-M spaces
	e. Pronotal light stripe wider, margins of prontal disk usually light
2a(1a)	a. Irregular network of supplementary crossveins present in the apical area of wings	Arcynopteryx compacta (McLachlan)
	also: Male of Epiproct of male long, needlelike
2b	a. Irregular network of supplementary crossveins absent in the apical area of wings	3
3a(2a)	Ab9 sternite produced posteriorly and recurved upward to that Ab10 is mostly or completely concealed	Males, 2
	Ab8 sternite not notched in the middle, or produced posteriorly over Ab9
3b	Ab9 sternite poorly or not produced posteriorly over Ab10, which is always visible	Females, 7
	Posterior margin of Ab8 sternite medially notched or produced posteriorly over Ab9
4a(3b)	Median ridge present between arms of mesoternal ridge	Isogenoides Klapálek
4b	Median ridge absent	5
5a(4b)	Well-defined mesal lobe on Ab7 sternum, often overlapping the anterior margin of Ab8 sternum	Cultus decisa (Walker)
5b	No mesal lobe on Ab7 sternum, often with an unpigmented zone	6
6a(5b)	Epiproct with lateral stylets, and narrowly pointed or subtriangular, apex entire	Hydroperla crosbyi (Needham and Claassen)
	also: Teeth projecting from the posteroventral surface of the epiproct small, < 0.5x as long as the apical hook; postocular areas of occiput lacking a dark mark
6b	Epiproct without lateral stylets, and with prominent lateral membranous lobes, apex of which bent strongly caudad	Helopicus nalatus (Frison)
7a(3b)	Median ridge present between arms of mesoternal ridge	Isogenoides Klapálek
7b	Median ridge absent	8
8a(7b)	Submental gills shorter, or absent	Cultus decisa (Walker)
8b	Submental gills long, at least 2x long as wide	9
9a(8b)	a. Subgenital plate usually reaching beyond the middle of Ab9 sternum, broadly rounded	Helopicus nalatus (Frison)
	b. Mesosterna with a transverse dark band
9b	a. Subgenital plate reaching at most the middle of Ab9 sternum, rounded	Hydroperla crosbyi (Needham and Claassen)
	also: Ab10 sternum with a pair of brown spots or areas
10a(1b)	Females (need to associate specimens with males for identification)	Clioperla clio (Newman), Isoperla Banks
10b	Males	11
11a(10a)	Ab10 tergum with elevated ridges on its hind margin	Clioperla clio (Newman)
11b	Ab10 tergum without elevated ridges	Isoperla Banks

Mature nymphs
(adapted from Stewart and Harper 1996, Stewart and Stark 2000)

1a	Lacinia unidentate	Isoperla Banks (in part)
	also: Abdomen with dark longitudinal pigment bands
1b	Lacinia bidentate	2
2a(1b)	Abdomen with dark longitudinal pigment bands	Isoperla Banks (in part)
2b	Abdomen without dark longitudinal bands	3
3a(2b)	a. Mesosternal Y-arms meet the anterior corners of furcal pits	Arcynopteryx compacta (McLachlan)
	b. Mandibles deeply cleft, separating teeth into two major cusps
	also: Ab1-3 divided by pleural fold
3b	a. Mesosternal Y-arms meet or approach posterior corners of furcal pits	4
	b. Mandibles not deeply cleft
4a(3b)	a. Mesosternum with a median longitudinal suture connecting fork of Y-arms with a transverse suture	Isogenoides Klapálek
4b	a. Mesosternum without a median longitudinal suture	5
5a(4b)	Submental gills conspicuous, projecting portion usually 2x or more as long as its basal diameter	6
5b	Submental gills absent, or barely projecting beyond submentum	7
6a(5a)	a. Transverse dark pigment bands of frons lateral to the median ocellus interrupted by circular yellow areas	Hydroperla crosbyi (Needham and Claassen)
	b. Ventral lacinial surface with an outer patch of about 10 setae
	c. Right mandible with 4 teeth
6b	a. Transverse dark pigment bands of frons uninterrupted by enclosed yellow areas	Helopicus nalatus (Frison)
	b. Ventral lacinial surface without an outer patch of setae
	c. Right mandible with 5 teeth
7a(5b)	Occiput and anterolateral prothoracic margins without rows of short, stout setae, although a few long setae may be present	Cultus decisa (Walker)
7b	Occiput or anterolateral prothoracic margins, or both, with a row of short, stout setae	8
8a(7b)	Ocellar region transversed by a dark band connecting the lateral ocelli and eyes, but not covering the anterior ocellus	Clioperla clio (Newman)
8b	Ocellar triangle more or less completely covered by dark pigment	Isoperla Banks (in part)

References

Kondratieff BC. 2004. Perlodidae - Perlodinae (The Springflies), pp. 149-180 in Stark BP, Armitage BJ (eds.), Stoneflies (Plecoptera) of Eastern North America, Volume II: Chloroperlidae, Perlidae, and Perlodidae (Perlodinae). Bulletin of the Ohio Biological Survey New Series Volume 14 Number 4. vi + 192 p.
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: September 26, 2006 - Last updated: November 7, 2013 (EB)