Orb-weaver Spiders

Sunday, May 20, 2007

Delta Journal
by Bob Thomas

Virtually any spider that constructs a rounded web may be properly called an orb spider, since the name of such a web is an orb. There are, however, some spiders that may be commonly called Orb-Weaver Spiders (these include the locally common genus Araneus, Family Araneidae).

There are several species in the New Orleans area. One has a brown abdomen, another has an olive drab abdomen with a white lichen-like pattern, and the most incredible one has a yellow abdomen with white spots and red legs with black bands at the joints. Wow!

The web is constructed to catch the spider’s prey. They have very poor vision, and find their prey by feeling the vibrations in the web. They securely wrap the prey (by turning it with the front legs and wrapping the silk with the fourth legs), bite it, then remove it to another place on the web and consume it.

Araneus webs are easily recognized. They are constructed almost vertical, and are rather delicate and easily damaged. As a result, there is usually daily repair work to do. Since the spider invests very little energy in actual construction, she must invest considerable time during the season to keeping the web up, including often completely rebuilding. An adult spider will construct an orb of about three feet in diameter. The very center will have an opening about the size of a quarter. During the evening hours, the spider positions itself over the opening in the center and waits for prey to hit the web. She rapidly assesses where it is and quickly moves to wrap and otherwise immobilize it.

During the day, the spider leaves the web (where she would be an easy target for predators) and move up one of the guy lines to some curled leaves where she has fashioned a hibernaculum, her little daytime resting place. When you see one of these webs during the day, you can almost always find the spider by looking up to find the obvious resting web.

Araneus and their relatives will usually run up to the hibernaculum if bothered, but they may also drop to the ground (or your head!) on a line of silk. They also have large fangs and a stinging, though not deadly, form of venom. Put these things together and you have a really creepy spider! But, remember, they are very important in their ecosystem.

Article Title: 
Orb-weaver spiders, Delta Journal, The Times-Picayune, May 20, 2007, C9