Darwin's Bark Spider (Caerostris darwini) is an orb-weaver spider that produces one of the largest known orb webs, ranging up to 2,8 square metres, with anchor lines spanning up to 25 metres.
The spider was discovered in Madagascar in the Andasibe-Mantadia National Park in 2009.
Its silk is the toughest biological material ever studied, over ten times tougher than a similarly-sized piece of Kevlar.
The species was named in honour of the naturalist Charles Darwin, with the description being prepared precisely 150 years after the publication of The Origin of Species, on 24 November 2009.
Like other spiders of the genus, they display extreme sexual dimorphism, with large females and small males.
Females vary in total body length from about 18 to 22 mm, males being around one third or less of this length, at about 6 mm. 
Females are largely black while males are redder and lighter brown in colour.
The first 3 photos show clearly the femora (third leg segment) of the legs being red and hairless.

Top, Left & Middle: A male. Mananara Lodge area, Anjozorobe, Madagascar, 17 January 2014
Right: A female. Andasibe-Mantadia National Park, Madagascar, 10 January 2014