Tuesday, May 31, 2011

The Writing Spider




Though often hidden, spiders make their homes within our own, and we find their delicate webs of intricate design nestled in ceiling corners and bushes that line our walkways. One particularly eye catching web is made up by the members of the genus Argiope - many of the species that comprise Argiope are brightly colored, and can be found across North America. The spiders belonging to Agriope form bright white lines on their webs called stabilimentum. They usually form an X in the middle the web, thus giving them the name the “writing spider” as their web designs resemble human handwriting. Unlike most spiders, Argiope do not eat their webs at night; instead, if a predator attacks, they rock their web back and forth presumably in an attempt to avoid being eaten.

Males are smaller than females, and form companion webs to the female before mating. After mating, female forms a large silken egg sack that she attaches to nearby plant material. The female then dies shortly after, and the juveniles emerge during the summer and become fully mature by fall. The average life span for Argiope is one year.

An example of Argiope that is common to San Diego is the Silver Argiope, which are distinguished by their banded silver legs and silver abdomen. They can be found in the Ecological reserve on campus, or in home gardens (particularly in prickly pear cactus, a favored plant of theirs).