The Arrow-shaped Micrathena spider is an orb-weaver with which many August hikers are all too familiar. This little guy—actually, more likely a girl—weaves its circular web across innumerable places in the forest, and, all too often, right across a trail. While the spiders are quite striking, with their black and gold colors on their bottom sides and bright yellow above, they're not much bigger than a dime, so you don't see them until you've walked through their webs and, if the spider's a little too slow to react, gotten them on your clothes, much to the consternation of hiker and inadvertent hitch-hiker. No harm done, of course—just annoyance on your part and wasted effort on the part of the spider.