Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
Perlidae (Stones) of Michigan - Identification
[under construction] Perlidae are generally our largest predacious stoneflies, and are especially common in cool to cold streams or rarely in wind-swept portions of clean lakes. Most species in Michigan are semi-voltine, especially towards the north, although some taxa that occur in clean warmer streams (e.g., Perlinella, Attaneuria, Neoperla, Perlesta) are probably univoltine in our area. Paragnetina media, on the other hand, appears to be broadly tolerant of most river conditions, and is probably our most common perlid.
Mature nymphs (adapted from Stewart and Stark 2000)
Stark and Szczytko (1981) provided a more recent description of this species, the only one of five Nearctic species found in Michigan. This species is more or less found throughout the state in most warm and cold running waters.
Male. Body: Length 11-16 mm; forewing 14-16 mm. General color dark brown. Abdomen: Terga 7-8 with mesal sclerites; spinule patches typically present on terga 6-9; sterna 3-8 with mesal patches of long setae; pleura 6-9 typically with lateral brushes; apical section of aedeagus bly armed ventrally, laterally with prominent, sharply pointed, triangular spines; largest spines long and slender, located in the apical third of the aedeagus.
Female. Body: Length 21-24 mm; forewing 22-25 mm. General color dark brown. Abdomen: Sternum 8 with a small triangular subgenital plate; notch deep, broadly U-shaped; lateral margins of vagina constricted basally; dorsal surface lined mesally with small scale-like setae; vaginal accessory glands short; spermathecum membranous, with 3 accessory glands typically present.
Nymph. Body: Total length of mature nymph 15-25 mm (length of females > males). General color dark brown patterned with yellow. Head: Brown except for 5 small circular areas of light pigmentation around the ocelli and tentoria. Mouthparts and setal patterns typical of genus. Abdomen: Dorsum unpatterned.
Egg. Outline oval, cross-section circular; chorion completely sculptured with a network of raised reticulation; collar long, slender and covered with irregular longitudinal ridges giving a twisted appearance; margin weakly and irregularly incised; micropyles small, arranged circumlinearly near the equatorial area; accessory micropylar structures consist of dorsally located shallow pits.
Stark BP, Guafin AR. 1976. The nearctic genera of Perlidae (Plecoptera). Miscellaneous Publications of the Entomological Society of America 10(1):1-77.
Stark BP, Szczytko SW. 1981. Contributions to the systematics of Paragnetina (Plecoptera: Perlidae). Journal of the Kansas Entomological Society 54(2):625-648.
Stewart KW, Stark BP. 2002. Nymphs of North American stonefly genera. Second Edition. The Caddis Press: Columbus, Ohio. xii + 510 p.
Page created: November 16, 2003; Last edited: November 7, 2013 (EB)