Madagascar.
Fine-art photographic collection
Caerostris extrusa
A bark spider that helped reveal how gene expression can transform silk performance.
About this species
Caerostris extrusaButler, 1882
Information reviewed15 July 2026
Caerostris extrusa is a Madagascan bark spider closely related to Darwin’s bark spider. Comparative genomics showed that the two possess a remarkably similar toolkit of silk genes, yet use that toolkit differently.
Taxonomy
Animalia · Arthropoda · Arachnida · Araneae · Araneidae · Caerostris
Accepted Madagascan species, redescribed in the modern revision of Caerostris. · checked 2026-07-15
MadagascarBroad documented range and selected reference localities — not a complete occurrence map.
What makes this species remarkable?
It carries essentially the same known repertoire of major silk-protein genes as the record-breaking Darwin’s bark spider.
The enormous difference in silk toughness between the relatives is linked less to owning unique genes than to how strongly particular genes are expressed.
Its flattened, bark-like body and cryptic resting posture allow a large orb-weaver to disappear against tree trunks during daylight.