DESCRIPTION

A. trifolium is a spider. It builds an orb-web and is classified in a group of spiders called orb-weaver spider.
Color is a characteristic that may help to identify a spider. A. trifolium is orange (though it may show up in a green or purplish form). Its large, bulbous abdomen is similar to a pumpkin. Measuring a spider's length also helps in its identification. A. trifolium is large, compared to other spiders. Size is an important way of distinguishing one spider from another.
The abdomen also contains the stomach or crop. In the fall the abdomen and the entire spider grows quickly. The high vegetation the spider prefers produces an abundance of insect food; and in the fall there is a growth spurt when food is most plentiful. This sudden increase in size may be cause for the spider's "sudden" appearance. In fact, the spiders have been present all-year, but were much smaller and simply less noticeable. The spider tends to show up around Halloween - and that is how it got its common name "Pumpkin Spider."