Darwin's Bark Spider

Caerostris darwini — Darwin's bark spider — is one of the most extraordinary spiders ever discovered and the producer of the strongest known biological material on Earth. The species was discovered and described in 2010 by Ingi Agnarsson, Matjaž Kuntner, and Todd Blackledge in Andasibe-Mantadia National Park, Madagascar. Females spin the largest orb webs ever documented — individual webs measuring up to 2.8 m² in surface area and SPANNING UP TO 25 METERS across rivers and forest gaps. The webs are anchored to opposite riverbanks by single 'bridge lines' that the spider releases into the air and allows to drift on rising thermals across distances of up to 100 m before adhering to the opposite bank. The bridge silk has a tensile strength of approximately 520 megajoules per cubic meter — over 10x tougher than kevlar by weight and approximately 2x tougher than the previously-known toughest spider silk (golden silk orb-weaver, Trichonephila). The toughness combined with extensibility allows Caerostris webs to absorb the kinetic energy of large flying prey (mayflies, caddisflies, butterflies, dragonflies, even small bats and birds) without snapping. The species is endemic to Madagascar and is currently classified as Vulnerable by the IUCN due to ongoing habitat loss in the spider's narrow forest range. The biomechanical implications of Caerostris silk for biomimetic materials engineering have driven intense research interest since 2010, including transgenic silkworm lines engineered to produce Caerostris-like silk proteins.