Shamrock Orbweaver Araneus trifolium

These beautiful orb weavers are impossible to pin down—literally. Their abdomens come in beige, brown, yellow, or even greenish hues, making them easy to confuse with the orange pumpkin spider. But look for the distinctive white dots arranged like tiny shamrocks on their back—that's your giveaway. These spiders weave massive webs up to two feet in diameter to catch flying insects. Found throughout the USA and Canada, their bite is more painful than you'd expect, but it's harmless to humans—about as bad as a bee sting.