OGDENSBURG You might not know their name, but every spring along the St. Lawrence River typically brings swarms of caddis flies filling the air with millions of tiny wings.
But this year those swarms of bugs known locally as shad flies arent where they are usually found, and experts arent sure of the reason.
Clarkson biology professor Michael R. Twiss, director of the Great Rivers Center, said caddis flies are an important part of the regions ecosystem and an excellent way to judge the water quality of local rivers.
Because the bugs are extremely sensitive to pollution levels in the water, Mr. Twiss said, The fact that theyre in the water is good because it means the water quality is really good.
Yet caddis fly populations are not evenly distributed throughout the region. This year has seen swarms of them in Lisbon, for instance, but only a few in Ogdensburg.
Sallie McDonough Planty, an Ogdensburg native and a seasonal resident of the city, said she remembers an Ogdensburg Maples baseball game in the late 1940s or early 1950s that was called off thanks to a shad fly swarm.
This was a night game. We got out there at Father Martin Field – which we called Winter Park at the time – and the [shad flies] were so thick they had to call the game.
The swarms are no longer as dense in the city as they once were. Mrs. Planty said she remembers that business owners had to sweep the dead bugs out of doorways and shovel them off sidewalks. She said she wonders every spring where the shad flies have gone.
Mrs. Planty is not alone.
Steve F. VanderMark, a retired educator and entomologist from Cornell Cooperative Extension of St. Lawrence County, said unfortunately there hasnt been much study focusing on caddis fly populations.
He said he still has a few educated guesses about why their numbers have declined in and around Ogdensburg.
He said its possible, for instance, that their population may have shifted with changes in the weather since the 1940s and 50s.
Its also possible that the caddis flies in Ogdensburg were simply blown away by gusts one year and havent yet repopulated the area in the same large numbers.
Another possibility, Mr. VanderMark said, is that the lights of the city drew them inland over the years and they failed to make it back to the water to lay their eggs, slowly killing off the local population.
The worst-case scenario, however, is water pollution, Mr. VanderMark said. Could they be telling us something? he said.
Mr. Twiss said that the water quality of the St. Lawrence River is not closely monitored, and that perhaps the caddis fly depopulation is an early warning sign.
They can be used as a water quality indicator, Mr. Twiss said. If theyre missing, there could be a reason theyre not around. People are right to be concerned about it.
But their numbers are still strong in Lisbon and over to Red Mills, said Lisbon native Michael J. ONeil, director of Lisbon Beach and Campground.
Mr. ONeil said he remembers having to sweep them off the porch of his St. Lawrence River camp when he was young, just like sweeping snow off your steps.
The bugs are interesting for several reasons, Mr. VanderMark said. To begin with, caddis flies differ from real shad flies (also known as mayflies) in several ways, the most notable of which is their wings.
Caddis flies have tent-shaped wings while shad flies hold their wings over their backs like sails on a boat, Mr. VanderMark said. Shad flies also dont emerge in large clouds as caddis flies do, and caddis flies spend most of their lives underwater as larvae.
Mr. Twiss said the caddis fly, which doesnt have a functional mouth, only emerges from the water as a flying insect to mate, lay eggs and die.
Theyre just built for sex, he said, adding that the reason they emerge in such great numbers all at once is so they are certain to reproduce even if a large number is eaten or killed.