of mayflies not harmful -- just creepy
By Rob Amen
Valley News Dispatch
They may bug you, but an expert who studies mayflies,
which once again have descended upon the Valley, said
they will cause you no harm.
Mayflies are large, transparent-winged insects that rise
from river bottoms, float on the surface and mate in the
air before dying, usually within 72 hours. Their appearance
in the Pittsburgh area -- you'll remember they hovered,
then covered, PNC Park during a Pirates game a couple
years back -- signals clean, viable waterways.
And contrary to popular opinion, they are not mosquitoes;
they don't bite; and you cannot contract West Nile Virus
"They really don't do anything in terms of harming
anyone. They may be more of a nuisance to some people,"
said Edwin C. Masteller, emeritus professor of biology
at Penn State, Behrend, who studies aquatic insects. "What
it means is there's a lot of food for fish. As they're
coming up the water, I'm sure a lot of fish are feeding
Masteller said mayflies typically spend two to three
years as nymphs in water such as Pittsburgh's three rivers
or Lake Erie before ascending to the surface. After they
fly away, they mate; females lay their eggs -- as many
as 8,000 -- on the water's surface, then die, along with
Reports have suggested mayflies were scarcely seen in
the Pittsburgh area during the past 150 years, and Masteller
said they were absent from the Erie area dating to the
1950s before beginning to emerge in 1997. By 1999, mayflies
had become a common sight around the lake. Masteller said
local meteorologists even included Doppler radar showing
echoes of large swarms of mayflies during television newscasts.
Mayflies in Pittsburgh, which Masteller said likely are
a different genus and species than those in Erie, began
noticeably surfacing in 2001. As long as they deem the
waterways clean, they'll probably stick around, Masteller
But he reiterated that they are harmless.
"They won't bother you at all," Masteller said.
"Their only intent is to find a mate."