Fleas hitch a ride on pets and wildlife, then infest carpets and bedding. They reproduce explosively and bite people and animals alike.

Tiny (about 1/8"), dark, wingless, and built to jump. You'll often spot them on pets or as fast-moving specks on light flooring.
What attracts them: Pets, wildlife (raccoons, opossums, strays) nesting nearby, and warm, humid conditions.
Fleas have a stubborn life cycle in carpets and cracks — professional treatment breaks the cycle that vacuuming alone can't.