June, 2009

Giant Lichen Orbweaver

Orbweavers in our area range from miniscule to enormous. While not the largest in terms of leg span or body length, the giant lichen orbweaver (Araneus bicentenarius) is certainly the heaviest. It is usually about an inch long and very robust. Some orbweavers can be found in their webs at all times, but this species is one of those that hides in a retreat at the edge of its web during the day. More frequently encountered are the enormous webs, which often span a gap of 8 feet or more. By following the main lines of silk to their upper anchors, it is usually possible to find the spider in its hiding place. The probable reason for this spider's nocturnal habit is bird predation. The markings on the backs of these spiders vary considerably, but always blend in very well with their surroundings, so they do well to remain still and nearly undetectable in their tree limb hideaways.

A fairly common species, I usually find several giant lichen orbweavers each year, always in wooded areas where they are likely to find high branches in which to make their webs, and where their camouflage will blend in with the bark, twigs, and lichens. Like many orbweavers, the females are the ones most noticed, with the males being much smaller. The females live longer than males, but still only one year, and by midsummer most are gone from their webs.

This spider is found in much of the eastern U.S.; the species name comes from the fact that it was discovered and named during Philadelphia's bicentennial celebration.