When cicadas emerge, they look for trees. They don't like hanging out on the ground.
So why does it feel like you're a magnet for the big, flying insects? The answer is simple:
"Cicadas land on people because they strongly resemble trees," explained Eric Day, an entomologist and cicada expert at Virginia Tech. (Mashable)
Don't worry though, they're completely harmless. But that doesn't stop me from freaking out if one's coming at me :)