Aquatic Insects of Michigan

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

Isonychiidae of Michigan - Identification

Introduction

Under construction

Adults (Imagoes, adapted from Kondratieff and Voshell (1984))

1a	Males	2
1b	Females	5
2a(1a)	a. Subgenital plate broadly concave, or with only a slightly posteromedian emargination	Isonychia (Prionoides) sayi Burks
	b. Penes dorsally with acute scleotized lateral and marginal serrations on incurved flap
	also: Caudal filaments whitish with no dark articulations
2b	a. Subgenital plate with a deep posteromedian emargination	3
	b. Penes dorsally without an incurved flap bearing sclerotized teeth or serrations subgenus Isonychia
3a(2b)	a. Penes without a prominent, lightly sclerotized dorsal flap or roll at the medial edge, at most with only a slightly sclerotized medial margin	Isonychia (>Isonychia) sicca (Walsh)
	b. Ventral lobes broadly to narrowly rounded posteriorly
3b	a. Penes with a prominent, lightly sclerotized dorsal flap or roll at the medial edge	4
	b. Ventral lobes with the posterior margin usually undulate
	also: Apical third to half of forewing hyaline, occasionally very faintly tinged with reddish-brown; Venation whitish to brown with costal and subcostal spaces of forewing not tinged with red or reddish-brown
4a(3b)	a. Penes dorsally without a basal dome-like swelling, at most only with lateral ridges	Isonychia (Isonychia) bicolor (Walker)
	b. Venation of forewings whitish to brown, with stigmatic region usually with no or few anastomosed crossveins
	c. Abdominal terga usually dark reddish-brown, occasionally orange
4b	a. Penes dorsally with a basal dome-like swlling forming lateral and apical ridges	Isonychia (Isonychia) rufa McDunnough
	b. Venation of forewings whitish to light yellowish, with numerous stigmatic crossveins usually anastomosed
	c. Abdominal terga usually bright red to reddish-orange brown
5a(1b)	a. Subanal plate with no, or only a shallow, posteromedian emargination	Isonychia (Prionoides) sayi Burks
	b. Eggs biconvex
5b	a. Subanal plate with a moderate to deep posteromedian emargination	Isonychia (Isonychia) sicca (Walsh), Isonychia (Isonychia) bicolor (Walker), or Isonychia (Isonychia) rufa McDunnough (cannot be further differentiated without associated males)
	b. Eggs spherical

Mature Nymphs (adapted from Kondratieff and Voshell 1984)

1a	Abdominal gill lamella without apical stout marginal spines	Isonychia (Prionoides) sayi Burks
1b	Abdominal gill lamella with a apical stout marginal spines	2
2a(1b)	Sclerotized distal edge of anterior margin of abdominal gill lamellae 6-8 usually with > 3 indistinct rows of stout spines, and a median sclerotized ridge usually with a row of spines along the entire length	Isonychia (Isonychia) sicca (Walsh)
2b	Sclerotized distal edge of anterior margin of abdominal gill lamellae 6-8 usually with < 2 indistinct rows of stout spines and a median sclerotized ridge usually only with scattered stout spines	3
note: unless nymph is associated with a male adult, couplet 2 requires slide mounting one nymphal gill lamella from Ab6-8 and examining with a compound microscope at magnifications of > 150-200x
3a(2b)	Ventral cleft of metathoracic femur usually with > 6 stout marginal spines (at least on one leg)	Isonychia (Isonychia) bicolor (Walker)
3b	Ventral cleft of metathoracic femur with usually < 5 stout marginal spines	Isonychia (Isonychia) rufa McDunnough

References

Kondratieff BC, Voshell JR, Jr.. 1984. The North and Central American species of Isonychia (Ephemeroptera: Oligoneuriidae). Transactions of the American Entomological Society 110: 129-244.

Page created: October 12, 2003; Last edited: November 06, 2013 (EB)