They are small flies, around 2-4mm long, and usually black/grey. They have an arched thorax giving a 'hump-backed' appearance, and have short, hairless antennae.
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They are small flies, around 2-4mm long, and usually black/grey. They have an arched thorax giving a 'hump-backed' appearance, and have short, hairless antennae.
==Life cycle==
==Life cycle==
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Eggs are laid on plants or stones under flowing water. The eggs hatch and develop into larvae, which attach to submerged rocks and pupate. They then pupate in a conical shaped cocoon. The adults then emerge later.
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Eggs are laid on plants or stones under flowing water. The eggs hatch and develop into larvae, which attach to submerged rocks and pupate. They then pupate in a conical shaped cocoon. The adults then emerge later.
The complete life cycle takes '''1 month''' to complete.
The complete life cycle takes '''1 month''' to complete.