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Animal profile

Darwin's Bark Spider

Caerostris darwini

ArachnidaRiver margins and lake edges in humid forest, with webs suspended over open water

Field profile

An orb-weaver described in 2010 and known for building the largest orb webs recorded, strung across rivers on anchor lines many metres long. Females are far larger than males. The silk it draws has the highest measured toughness of any known biological material.

Scope note

This is an editorial profile, not a diagnostic field-identification guide or a substitute for current conservation assessments. Follow the cited sources on each fact for the evidence trail.

Published field notes

2025-01-24

Darwin's Bark Spider

One spider bridges rivers with silk

Anchor lines of up to twenty-five metres carry the web of Darwin's bark spider clear across Madagascan rivers, holding an orb of up to about 2.8 square metres in open air where flying insects concentrate.

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Darwin's Bark Spider | Daily Animal Facts