Most swarming occurs in late June and early July.
Mayflies accumulate around lights, making roads, streets, sidewalks, etc. slippery and dangerous.
These annoying insects may fly into one's face, ears, hair, land on clothing, crawl behind eyeglasses and splatter car windshields. Along lake shores, piles of decaying bodies drift onto beaches and, if not removed, an offensive fish-like odor occurs discouraging tourists during the July 4th holidays. Mayflies do not bite or sting nor feed on homes, furnishings, food, etc. The chief importance lies in their value as food for fish, dragonfly nymphs and birds. Antennae are short inconspicuous bristles.