Plecoptera - Stoneflies

Introduction

Stoneflies are primarily associated with clean, cool-to-cold running waters, although a number of species are adapted to large, oligotrophic boreal and alpine lakes. Species of Plecoptera are often associated with clean water qualities, and their presence or unnatural absence is often a key component of water quality indices. Nymphs tend to have specific water termperature, substrate and food types, and stream size requirements, reflected in their distribution along the source of river longitudinal continuum. There are also distinct microdistributions for size classes within individual species. Although distributed world-wide, Plecoptera are associated with cooler water temperatures and, consequently, distribution tends to be amphipolar. Currently, there are 59 species of Plecoptera reliably recorded from Michigan (Grubbs and Bright 2003).

Adults (based on Poulton and Stewart 1991, and Stewart and Harper 1996)

1a	Paraglossae and glossae about equal length	2
1b	Paraglossae longer than glossae	6
2a(1a)	Gill remnants on sides of thorax and Ab1-2	Pteronarcyidae
	also: three ocelli; 2 rows of anal cross veins in forewing; very large, > 45mm length
2b	Gill remnants absent from Ab1-2, but may be present elsewhere	3
3a(2b)	Tarsal segment 2 subequal to segment 1	Taeniopterygidae
3b	Tarsal segment 2 much shorter than segment 1	4
4a(3b)	a. Cerci with many segments	Capniidae
	b. In forewing, 2A simple and unforked
	c. Intercubital crossveins few, usually 1-2
4b	a. Cerci of one segment, often globular	5
	b. Vein 2A in forewing forked, usually 5 or more
5a(4b)	a. Wings folded flat over back at rest	Nemouridae
	b. Forewing with vein in costal space beyond cord, forming with adjoining veins a X-pattern
	c. Terminal segment of labial palpus circular and larger than preceding segment
5b	a. Wings rolled at rest, covering sides and back of abdomen, giving insect a sticklike appearance	Leuctridae, Leuctra Stephens
	b. Forewing without vein in costal space beyond cord
	c. Terminal segment of labial palpus more elongate, not much larger than preceding segment
6a(1b)	a. Gill remnants on side of thorax	Perlidae
	b. Cubito-anal crossvein of forewing reaching anal cell, or not distant from it by more than its own length (may not always be reliable)
6b	a. Gill remnants absent from thorax	7
	b. Cubito-anal crossvein of forewing, if present, usually removed from anal cell by at least its own length
7a(6b)	a. Vein 2A of forewing leaves anal cell as 2 separate veins (set in anal cell)	Perlodidae
	b. Hindwing with 5-10 anal veins
	c. Body color in life variable, most species with amber to dark wings
7b	a. Vein 2A of forewing forked beyond anal cell (set beyond anal cell)	Chloroperlidae
	b. Hindwing with fewer than 5 anal veins
	c. Body yellow or green in life, pale in alcohol, wings clear

Nymphs (based on Poulton and Stewart 1991, and Stewart and Stark 1988)

1a	Highly branched gills present on sides and venter of all thoracic segments	2
1b	Gills absent, or restricted to cervical or coxal area, or fingerlike without numerous filaments	3
2a(1a)	a. Branched gills on both thorax and sterna of Ab1-2	Pteronarcyidae
	b. Paraglossae and glossae about equal length, set at approximately same level on labrum
2b	a. Branched gills absent from sterna of Ab1-2	Perlidae
	b. Paraglossae longer than, and set above, the glossae
3a(1b)	a. Coxae with single, finger-like gills, or abdomen with large triangular ventroapical plate	Taeniopterygidae
	b. Tarsal segments 1 subequal to segment 2
3b	a. Coxal gills and ventroapical abdominal plates absent	4
	b. Tarsal segment 2 wedgeshaped, and shorter than segment 1
4a(3b)	Apex of labial palps extending little beyond the anterior paraglossal margin	5
	paraglossa and glossa extending forward about the same level on labrum
4b	Entire apical semgent of labial palp extending beyond anterior margin of paraglossa	7
	paraglossa longer than, and set above, glossae
5a(4a)	a. Metathoracic wingpads strongly divergent from body axis	Nemouridae
	b. Body short, hind legs when extended reach tip of abdomen
	also: Branched cervical gills sometimes present
5b	a. Wing pads nearly parallel to median body axis	6
	b. Body elongate, hind legs when extended do not reach tip of abdomen
6a(5b)	a. Setae absent, or sparse, on posterior margin of abdominal terga	Leuctridae, Leuctra Stephens
	b. Distance between tips of front wing pads greater than distance between tips of hind wing pads
	c. Membranous pleural fold reaches from first abdominal segment to, at most, Ab7
6b	a. Setae present on posterior margin of abdominal terga	Capniidae
	b. Distance between tips of front wing pads about equal to distance between tips of hind wing pads
	c. Membranous pleural fold reaches to Ab9
7a(4b)	a. Length of cerci 3/4 or less than length of abdomen	Chloroperlidae
	b. Terminal segment of maxillary palp usually much thinner than preceding segment, typically set asymmetrically on penultimate segment
	c. Axis of wing pads nearly parallel to body axis
	d. Body pigment contrast weak or absent
7b	a. Length of cerci as long or longer than length of abdomen	Perlodidae
	b. Terminal segment of maxillary palp only slightly thinner than preceding segment
	c. Axis of hindwing pads markedly divergent from body axis
	d. Body pigment contrast present

References

Grubbs, SA., Bright, E. 2003. Arcynopteryx compacta (Plecoptera: Perlodidae), a Holarctic stonefly confirmed from Lake Superior, with a review and first checklist of the stoneflies of Michigan. The Great Lakes Entomologist 34(2):77-84.
Poulton BC, Stewart KW. 1991. The stoneflies of the Oaark and Ouachita Mountains (Plecoptera). Memoirs of the American Entomological Society 38. ii + 116 pp
Stark BP, Nelson CR. 2002. The Nearctic Plecopteran families: morphology and systematics, pp. 11-28 in Stark BP and Armitage BJ (editors), Stoneflies (Plecoptera) of Eastern North America. Volume 1. Pteronarcyidae, Peltoperlidae, and Taeniopterygidae. Bulletin of the Ohio Biological Survey, New Series 14(1). vii + 100 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. 1988. Nymphs of North American stonefly genera (Plecoptera). The Thomas Say Foundation Volume 12. xiii + 460 p.

Page created: May 15, 2003 (EB) - Last updated: September 27, 2006 (EB)