Aquatic Insects of Michigan

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

Taeniopterygidae (Winter Stoneflies) of Michigan - Identification

Introduction

Three genera and 6 species are recorded from Michigan, out of 6 genera and 34 species currently described from North America. These stoneflies are part of the "winter stonefly" fauna, with adult emergence usually beginning in late February through April (depending on species and temperature/degree days). All species appear to be univoltine in our state, with a summer diapause and rather fast growth in late fall and winter. Species of Taeniopteryx are very common constituents of leaf packs, woody debris and riffle areas both warm and cold-water streams in our state where water quality is not too seriously impared. Strophopteryx and Oemopteryx are found in colder streams, and are less common.

Adults
(adapted from Stewart 2000)

1a	Males	2
1b	Females	8
2a	a. In lateral view, Ab9 sternum produced little, if any, beyond the posterior margin of Ab10, and is not scoop-shaped	Taenioptyeryx Banks, 4
	b. A single cercal segment with no basicercal process
	c. Ventral, membranous coxal gill scars usually evident, appearing as pale circular membranes
2b	a. In lateral view, Ab9 produced well-beyond the posterior margin of Ab10, scoop-shaped	3
	b. At least 5 cercal segments, with a basicercal process present on the first cercal segment
	c. No gill scars present on coxae
3a(2b)	a. Epiproct with wide anterior and posterior prongs, expanded laterally at their tips	Oemopteryx glacialis (Newport)
	b. In lateral view, posterior (produced) portion of Ab9 sternum thick, but little, if at all, upturned
	c. Fore wings brachypterous
3b	a. In dorsal view, epiproct with a single prong, not as above	Strophopteryx fasciata (Burmeister)
	b. In lateral view, posterior (produced) portion of Ab9 sternum relatively thinner, with a markedly upturned tongue
	c. Fore wings of normal size, not reduced
4a(2a)	Vesicle present on Ab9 sternum	5
4b	Vesicle absent on Ab9 sternum	7
5a(4a)	a. Vesicle length < 2.75x its greatest width	Taeniopteryx nivalis (Fitch)
	b. Ab9 sternum with apical (posterior part of sternum) hairs directed down and forward, and shorter than the more anterior hairs
5b	a. Vesicle longer, length 3-5x its greatest width	6
	b. Ab9 sternum with apical hairs directed backward, and are as long or longer than the more anterior hairs
6a(5b)	a. Hind femura with a posteromedial spur projecting a distance at least half as much as the width of the femur	Taeniopteryx maura (Pictet)
	b. Posteromedial arms of paraprocts narrowly triangular with acute apices
6b	a. Hind femura without a posteromedial spur, or a callus or spur projecting less than half the width of the femur	Taeniopteryx burksi Ricker and Ross
	b. Posteromedial arms of paraprocts fingerlike, with nearly parallel sides and subtruncate apices
7a(4b)	Posterior projection of paraprocts thick, with acute, outward-hooked tips	Taeniopteryx parvula Banks
7b	Posterior projection of paraprocts with rounded, finger-like unhooked tips	Taeniopteryx metequi Ricker and Ross
8a(1b)	a. Ab9 sternum not reaching the subanal lobes	Taenioptyeryx Banks, 10
	b. Ventral, membranous coxal gill scars usually evident, appearing as pale circular membranes
8b	a. Ab9 sternum produced well beyond the bases of the subanal lobes	9
	b. No gill scars present on coxae
9a(8b)	a. Ab9 sternum reaching only to the cercal bases	Oemopteryx glacialis (Newport)
	b. Ab8 sternum of two well-defined lateral plates and a distinctive median subgenital plate on a membranous background
9b	a. Ab9 sternum reaching well beyond the cercal bases	Strophopteryx fasciata (Burmeister)
	b. Ab8 sternum uniformly sclerotized notched posteromedially and usually with a faint pattern of transverse striations
	also: Genital notch of Ab8 sternum V-shaped, widened posteriorly
10a(8a)	a. Middle half of Ab8 sternum little sclerotized, light in color	Taeniopteryx parvula Banks
	b. Subgenital plate with a dark V
10b	a. Middle half of Ab8 sternum normally sclerotized, often lighter anteromedially	11
	b. Subgenital plate not scleritized as a dark V
11a(10b)	A tongue-like, lightly sclerotized plate in the genital notch	12
11b	No tongue-like plate in the genital notch	13
12a(11a)	Subgenital plate with a median, nipple-like projection	Taeniopteryx burksi Ricker and Ross
12b	Subgenital plate apically truncate and shallowly concave also: genital notch with a dark, broadly V-shaped margin	Taeniopteryx metequi Ricker and Ross
13a(11b)	Sclerotized shoulders of the genital notch meet anteriorly to form an acute angle	Taeniopteryx nivalis (Fitch)
13b	Sclerotized shoulders of the genital notch lightly sclerotized anteriorly, appearing as a thin line and not appearing to meet at an angle	Taeniopteryx maura (Pictet)
	also: A pair of light plates in the genital notch

Mature Nymphs
(adapted from Fullington and Stewart 1980, Poulton and Stewart 1991, Stewart and Stark 2002)

1a	A. Single, finger-like gill on each coxa	Taenioptyeryx Banks, 3
	b. Often a prominent middorsal stripe on at least the thorax and abdomen
1b	No coxal gills present	2
	b. Various patterned, but not with a prominent middorsal stripe
2a(1b)	a. Tibiae with both an inner (ventral) and outer (dorsal) hair fringe	Strophopteryx fasciata (Burmeister)
	b. Single, short dorsal hair present on basal cercal segments
	c. Clothing hair on basal half of Ab9 sternum sparse
2b	a. Tibiae with only an outer (dorsal) hair fringe	Oemopteryx glacialis (Newport)
	b. 1-3 fine dorsal hairs present on basal cercal segments
	c. Clothing hair on basal half of Ab9 sternum numerous
Generally the key below for Taeniopteryx applies to male nymphs, distinguished by the developing epiproct
3a(1a)	Middorsal stripe absent or incomplete	3
3b	Middorsal stripe complete, extending the length of the thorax and abdomen, sometimes on the head capsule	5
4a(3a)	a. Pronotum margined with yellow	Taeniopteryx parvula Banks
	b. Dark mottling on occiput
	c. Legs concolorous
	d. Abdominal terga with long, curved setae and occasional fine hairs
	e. Developing epiproct triangular when viewed dorsally, terminating in a bulbous knob
4b	a. Pronotum only laterally margined with yellow	Taeniopteryx nivalis (Fitch)(in part)
	b. Occiput without dark mottling, or if present indistinct
	c. Legs with apex of femora yellow
	d. Abdominal terga with short, blunt bristles and occasional long hairs
	e. Developing epiproct triangular when viewed dorsally, with no terminal bulbous knob
5a(3b)	No yellow area between the eyes	Taeniopteryx nivalis (Fitch) (in part)
	also: Head with faint mottling sometimes present on the occiput, but usually dark, concolorous; abdominal terga with faint, yellow spots
5b	Middorsal stripe extending onto the head capsule as a yellow area between the eyes	6
6a(5b)	a. Pale area between the eyes wider than the pronotal portion of the middorsal stripe, interspersed with irregular mottling (muscle scars)	Taeniopteryx metequi Ricker and Ross
	b. Yellow ring around each eye broad
6b	a. Pale area between the eyes of the same width, usually with no visible interspersed mottlings (muscle scars)	7
	b. Yellow ring around each eye narrow or absent
7a(6b)	Male nymphs with the inner margin of hind femur with the adult's developing femoral spur visible beneath the exoskeleton	Taeniopteryx maura (Pictet)>
7b	Male nymphs with the inner margin of the hind femur without a developing femoral spur of the adult, at most with only a raised callous or spur	Taeniopteryx burksi Ricker and Ross

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