In 2004, when the cicadas of Brood X crawled out of the ground in and around Washington, Lori Milani, then a full-time student, would not set foot outside her apartment. Terrified of insects, she shut her windows tight, sometimes with the blinds drawn, for five weeks. She stocked up on food, canceled her summer classes and had friends run essential errands for her.

“It was truly horrible. I know that they are harmless, but they’re disgusting,” said Ms. Milani, who has suffered from a fear of bugs, or entomophobia, as long as she can remember.

This year’s 17-year swarm, called Brood II, has not yet arrived there, but as she ventures outside, Ms. Milani says, her heart races and she scans the trees and the grass for signs of movement. “I have made arrangements with my office to telecommute when they do emerge,” said Ms. Milani, who recently started a blog, cicadaphobia.com, to track their arrival so others can be warned.