Stoneflies (order Plecoptera) are aquatic insects known for their sensitivity to water pollution, making them important bioindicators of water quality. Here’s a detailed overview:

Key Characteristics:

Appearance: Slender, flattened bodies with long antennae and two pairs of membranous wings (held flat over the abdomen at rest). Adults resemble immature forms (nymphs).
Size: Typically 5–50 mm long, depending on the species.
Life Cycle: Incomplete metamorphosis (egg → nymph → adult). Nymphs live in clean, well-oxygenated water (streams, rivers) for months to years before emerging as short-lived adults (1–4 weeks).

Habitat & Ecology:

Nymphs: Require cold, fast-flowing, unpolluted water with high oxygen levels. They cling to rocks and feed on algae, detritus, or other insects (some species are predatory).
Adults: Poor fliers; often found near water on vegetation or rocks. They feed little or not at all.

Importance:

Bioindicators: Their presence signals healthy freshwater ecosystems; their absence may indicate pollution.
Food Source: Nymphs and adults are prey for fish (e.g., trout), birds, and other aquatic organisms.
Fishing: Nymphs are used as live bait or models for fly-fishing lures ("stonefly patterns").

Fun Facts:

One of the oldest insect orders, dating back over 300 million years (Carboniferous period).
Some species drum or vibrate to communicate during mating.
Over 3,500 species worldwide, with diversity highest in temperate regions.

Threats:

Pollution: Sensitive to pesticides, heavy metals, and organic waste.
Habitat Loss: Damming, urbanization, and climate change (warming waters reduce oxygen levels).

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