Plecoptera

Burmeister, 1839

stoneflies

Suborder Guides

Nemouroidea(Rolled-winged Stoneflies)
Perloidea(common stoneflies)
Pteronarcyoidea

, commonly known as , comprises approximately 3,500 described worldwide. This order represents one of the most primitive groups of Neoptera, with fossil relatives dating to the Carboniferous and Lower Permian periods, though modern diversity appears to be of Mesozoic origin. Stoneflies are found on every continent except Antarctica, with distinct in the Northern and Southern Hemispheres. All species are aquatic in their stages and are highly sensitive to water pollution, making them important bioindicators of stream and river health.

Soyedina interrupta by (c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon. Used under a CC-BY license.

Osobenus by (c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon. Used under a CC-BY license.

Yoraperla by no rights reserved, uploaded by Todd Folsom. Used under a CC0 license.

Pronunciation

How to pronounce Plecoptera: /plɛˈkɒptərə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are distinguished from similar aquatic insects by their long, multi-segmented (typically longer than body), two claws on each leg, and long paired . They differ from mayflies (Ephemeroptera) by holding wings flat over the body rather than upright, and by having chewing rather than mouthparts. They differ from caddisflies (Trichoptera) by having simple rather than hairy wings and lacking a coiled . Wingless may be confused with nymphs, but have fully developed genitalia and different body proportions.

Images

Habitat

Nymphs inhabit the benthic zone of well-oxygenated lakes and streams, requiring clean, fast-moving water with high dissolved oxygen. A few in New Zealand and nearby islands have terrestrial nymphs that inhabit only very moist environments. are found near water bodies, on stones, vegetation, bridges, and stream banks. Some species are exclusively aquatic throughout life, never leaving the water as adults.

Distribution

Worldwide distribution on all continents except Antarctica. are quite distinct between Northern and Southern Hemispheres, though evolutionary evidence suggests may have crossed the equator multiple times before becoming geographically isolated again.

Seasonality

Activity patterns vary by and climate. Winter stoneflies ( Capniidae and Taeniopterygidae) are active during winter months, often seen on snow-covered stream banks. of most species emerge during specific times of year when resources are optimal. Adults generally survive only a few weeks.

Diet

Nymphs: most are herbivorous, feeding on submerged leaves and benthic ; many are of other aquatic arthropods. : some feed on lichens, algae, or vegetation; others do not feed at all, having obtained all necessary nutrients as nymphs.

Life Cycle

Females lay up to one thousand , deposited directly into water or onto rocks and vegetation above water; eggs have a sticky coating to adhere to substrates. Eggs hatch in two to three weeks, though some undergo with eggs remaining through dry seasons. Nymphal stage lasts one to four years with 12 to 36 . Nymphs leave water, attach to fixed surfaces, and undergo final molt to become terrestrial . Adult lifespan is typically a few weeks.

Behavior

are generally weak fliers, with some preferring and running; a few species are attracted to lights. Males drum their against substrates (branches, stones) to create species-specific vibrational signals; females respond with their own drumming if receptive, leading to courtship duets. Winter-active species produce glycerol, proteins, and sugars that act as antifreeze compounds, preventing freezing death on snow and ice.

Ecological Role

are critical bioindicators of water quality; their presence indicates good or excellent water quality, while their absence suggests pollution, heavy sediments, or low oxygen. Nymphs and are important food sources for freshwater fish including trout and steelhead. Nymphs contribute to nutrient cycling in aquatic through herbivory and .

Human Relevance

Used extensively in biomonitoring and environmental assessment due to their sensitivity to water pollution. Popular among fly fishermen; numerous artificial lures mimic (e.g., Montana Stone Yellow, Henry's Fork Yellow Sally). Some attracted to porch lights and zappers.

Similar Taxa

Ephemeroptera (mayflies)Both orders have aquatic nymphs and are used in EPT water quality indices, but mayflies hold wings upright at rest, have mouthparts as , and possess only two or three tail filaments versus the paired of .
Trichoptera (caddisflies)Closely related and also used in EPT indices, but caddisflies have hairy wings, prominent maxillary and labial palps, and often build protective cases as larvae.

More Details

Etymology

The name '' derives from Ancient Greek plekein ('to braid') and pteryx ('wing'), referring to the complex venation pattern of the wings.

Evolutionary significance

are considered among the most primitive living groups of Neoptera, providing important insights into early winged insect evolution.

Aquatic adaptations

A few wingless , including Capnia lacustra and Baikaloperla, are among the only known insects that remain exclusively aquatic from birth to death, never becoming terrestrial as .