Mayflies fill the air near the Peoria, Ill., riverfront, Wednesday June 27, 2001, as they hatch by the millions along the Illinois River. Mayflies are from the insect order known as Ephemeroptera, a blend of the Greek words meaning ``a day's duration'' and ``wing.'' During their one-day lives, the flies exist largely to mate and are so focused on sex that their immature, non-sexually active phase can pass in as little as five minutes. Some mayflies even grow to their rapid adulthood without mouths or digestive systems so they don't spend valuable mating time on eating. (AP Photo/Journal Star, Ron Johnson)