Darwin's bark spider (Caerostris darwini) is an orb-weaver
spider that produces one of the largest known orb
webs, with anchor lines spanning up to 25 metres (82 ft). The spider
was discovered in Madagascar in
the Andasibe-Mantadia National Park in 2009.
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
silk is the toughest biological
material ever studied, over ten times stronger than a
similarly-sized piece of Kevlar.
The average toughness of the fibres is 350 MJ/m3, and some are up to 520
MJ/m3 making the silk twice as strong as any other spider silk known.
Several webs of C. darwini have been seen spanning a river,
demonstrating their extreme length. See photo, click for a
larger view. The web
of Darwin's bark spider is remarkable in that it has not only the
longest spanning web ever observed, but is among the largest orb webs
ever seen, at an area of up to 2.8 square metres (30 sq ft). Nephila
komaci, discovered in 2009, and some other Nephila species also make
webs that can exceed 1 m (3 ft 3 in) across.
According to professor Ingi Agnarsson, director of the Museum of Zoology
at the University of Puerto Rico, the spider's web occupies a unique biological
niche, stating: "They build their web with the orb suspended directly above a
river or the water body of a lake, a habitat that no other spider can use". This
position allows the spiders to catch prey flying over the water, with
webs observed to large web are thought to have coevolved at
the same time, as the spider adapted to the habitat. Scientists
are currently researching how the spider is able to weave such a large
web over water along with being able to anchor drag lines on either side
of a river.
other spiders of the genus, Darwin's bark spider displays extreme sexual
dimorphism, with large females (18 mm) and small males (6mm).
spider was described along with an undescribed species of fly, which
appeared to have a kleptoparasitic relationship
with it. The flies often feed on the spider's catches before the spider
wraps them. Occasionally, spiders have been observed to chase away the
flies when they land on something that the spider is eating.
Photo showing eyes. Click for a larger
Photo showing how the colour blends with the bark. Click for
a larger view.
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