Perlinella

This genus is an uncommon denizen of smaller streams in Michigan that are not largely impacted by human modification, but appears to be more commonly encountered in streams in states bordering our state. Two of the three species of Perlinella are recorded from Michigan (Grubbs and Bright 2003), with another species (P. zwicki) known only from the southeastern USA. Kondratieff et al. (1987) revised the genus, and the keys below are taken from this work. Nymphs are carnivorous, with chironomids and other invertebrates forming the basis of its diet (Frison 1935, Bright 1996).

Adults

1a	a. Paraprocts scleritized, arising from the cercal bases, with a hook-like apex recurved over the posterior margins of Ab10 tergum	Males, 2
	b. Ab8 sternum not modified, Ab9 sternum with a large oval hammer
1b	a. Paraprocts unmodified as above	Females, 3
	b. Ab9 sternum unmodified, Ab8 sternum with a short, bilobed subgenital plate
2a(1a)	a. A dark triangular spot in front of the clypeus and pronotum with a dark median stripe bordered by pale areas	Perlinella drymo (Newman)
	b. 3 ocelli
	c. Aedeagus with a dark sclerite expanded over the distal half, serrated laterally (usually 12-16 teeth) along the expanded lobe, usually truncated apically and terminating in an acute point mesoapically
2b	a. Pronotum without a distinct middorsal stripe, or if present no dark triangular mark in front of the clypeus	Perlinella ephyre (Newman)
	b. 2 ocelli
	c. In lateral view, the aedeagal sclerites expanded ventrally in the distal 1/4, serrated laterally along the expanded lobe, terminating in a sharp downturned darker hook on the inner margin, resulting in a claw-hammer shape in lateral aspect
3a(1b)	a. Three ocelli	Perlinella drymo (Newman)
	b. Subgenital plate with a broad median notch
	c. Spermathecum membranous, with 6 vaginal accessory glands present
3b	a. Two ocelli	Perlinella ephyre (Newman)
	b. Subgenital plate not as above, more rounded
	c. Spermathecum membranous, usually 4 short vaginal accessory glands present

Nymphs

1a	a. Anterior ocellus present (three ocelli) in mature nymphs	Perlinella drymo (Newman)
	b. Head and thorax usually with discernible dark and light pattern
1b	a. Anterior ocellus absent (two ocelli)	Perlinella ephyre (Newman)
	b. Head and body yellowish-brown, pronotum without a distinct pattern

References

Bright E. 1996. A new larval record of Perlinella drymo (Plecoptera: Perlidae) for Michigan. The Great Lakes Entomologist 29(1):39-42.
Frison TH. 1935. The stoneflies, or Plecoptera, of Illinois. Illinois Natural History Survey Bulletin 20:281-471.
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.
Kondratieff BC, Kirchner RF, Stewart KW. 1987. A review of Perlinella Banks (Plecoptera: Perlidae). Annals of the Entomological Society of America 81(1):19-27.

Page created: November 16, 2003 - Last updated: June 19, 2006 (EB)