July 04, 2013THE GROSSE POINTES — For mayflies, life is short and sweet.
"They only live one or two days," said Richard Merritt, distinguished professor and past chair of entomology at Michigan State University. "They mate and lay eggs in sediment."
Insects that Grosse Pointe residents traditionally call fishflies are a misnomer.
The accurate name is mayfly
Mayflies are smaller than fishflies and live a week.
Mayflies don't have mouths. Fishflies do. They eat aquatic plants and small animals, including tadpoles.
"Fishflies is a different order of insect, the megoloptera," Merritt said. "Their larvae are predators. They don't live in sediment."
Fishflies more commonly come from rivers, not lakes, he added.
Mayflies are another example every living thing serves to further the species and strengthen the food chain.
"They're a major source of food for fish," Merritt said.
"It's amazing how many organisms use this organism," said Donald Schloesser, a fisheries biologist in the Ecosystem Health and Restoration Branch of the U.S. Geographic Survey in Ann Arbor. "Spiders and gulls eat it. So do frogs, snakes and most birds."
Over thousands of years, nature set the biological clocks of certain species to the appearance of mayflies.
"Swallows nesting under finger piers at the (Grosse Pointe Farms) marina time hatchings to fish flies so they'll have lots of food to feed their young," said Bill Rapai, president of Grosse Pointe Audubon and a resident of the City of Grosse Pointe.
Male mayflies tend to be smaller and darker than females, Schloesser said. The female's wings lack black dots.
Many mayflies emerging en masse each summer from Lake St. Clair succumb at night to the lure of swarming streetlights.
During John Cottrell's junior high school years, mayflies on pavement beneath the lights felt the crush of his Stingray bicycle.
"I loved doing that," said Cottrell, now retired in Grosse Pointe Farms.
The snap, crackle and pop ended a cycle of life that began a year earlier, two if water temperatures weren't warm enough.
"The cycle consists of eggs being laid in about June," Schloesser said.
Mating occurs airborne over water. Females lay eggs in the water. Eggs sink and females die on the surface. Males die on land.
Eggs take about six weeks to hatch into larvae, which emerge from sediment.
"They go through a number of stages as immatures from September through May," Merritt said.
"We call them nymphs when they're in the water," Schloesser said. "They grow, reproduce and shed skin like a snake."
A series of incremental growth follows.
"By May or June, they're large enough to turn into the adult stage," Merritt said.
Water temperature in the mid-50-degree range triggers nymphs to exit the water and mate, Schloesser said.
"One warm day isn't going to make a difference," Merritt said. "It's the accumulation of heat from the time they start growing as larvae in sediment until that next spring or summer when they get enough heat in their body to come off as adults."
"They fly ashore," Schloesser said. "After about 24 hours, they shed another skin and turn into the adult, which is capable of reproduction. Then, the whole process starts over again."
Adults commonly emerge each summer in pulses.
"The pulse usually occurs over a two-to-three-week period," Schloesser said.
Scientists value mayflies as an indicator species of water quality.
"When Lake Erie basically died from pollutants, it killed the mayfly," Merritt said. "That was the first sign there was something seriously wrong with Lake Erie."
"In western Lake Erie, they were pretty much gone for close to 50 years," Schloesser said.
"It was cleaned up and mayflies came back," Merritt said.
"That, to me is proof in the pudding of their worth to society," Schloesser said.