In 1999, a local TV station's Doppler weather radar detected millions of mayflies heading for Presque Isle in blue and green splotches on the radar in clouds measuring long. These insects were a sign of Lake Erie's move back to health, since the mayflies require clean water to thrive. Biologist Masteller of Pennsylvania State University declared the bugs to be a "nice nuisance" since they signified the lake's return to health after forty years of absence. Each is long; the three main species of mayflies are "Ephemera simulans", "Hexagenia rigida" and "Hexagenia limbata". The insects mate over a 72-hour period from June through September; they fly in masses up to the shore, mate in the air, then females lay up to 8,000 eggs each over the water; the eggs sink back down and the cycle repeats. Sometimes the clouds of mayflies have caused power outages and roads to become slippery with squashed insects. Since zebra mussels filter extra nutrients from the lake, it allows the mayfly larvae to thrive.