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"Writing Spider"
Female Argiope with web stabilimenta, the heavy
white zigzag portions.
Stabilimenta are
conspicuous lines or spirals of silk, included by
many diurnal spiders at the center of
their otherwise cryptic webs. It has been shown
spider webs using stabilimenta catch, on average,
34% fewer insects than those without. However, webs
with the easily-visible markings are damaged far
less frequently by birds flying through the web. It
is an evolutionary tradeoff the spider can influence
every time it builds a new web. The inclusion of
stabilimenta is influenced by many factors,
including prey density and web location.
(1)
In any event, stabilimenta or no,
a large Argiope planted firmly head-down in her web
amongst tall weeds and grasses remains maddeningly
invisible to man and beast. The black and yellow
markings of the fat abdomen and striped legs
function as camouflage much like the tigers' stripes
do in the jungle - the geometric elements serve to
break up the outline of the spiders' body and
confuse the eye of the beholder into not recognizing
the image. It is this principle upon which warships'
hull camouflage was painted during the World Wars,
with stark diagonal lines and shapes intended to
keep an enemy from discerning the outline and
identifying the size of the ship and the extent of
its armaments. |
