Dark Fishflies

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Filed under Outdoor Notes

May 23, 2010

Dark Fish fly

Dark Fish Fly

The Dark Fishflies belong to the genus Nigronia . You tell them apart by the amount of white on their wings. Nigronia fasciatus has considerable white, almost a band, across the wing. Nigronia serricornis has less. This, then, I believe is N. serricornis..

Dark Fishflies spend most of their lives as aquatic larvae, which are familiar to fisherman as hellgrammites. They will actually only spend about ten days as adults, fluttering around on the edges of streams as they search for mates and, later, places to lay eggs.

The females will lay their eggs underneath leaves hanging some twelve to twenty feet above the stream. The eggs will hatch about two weeks later.

The hellgrammites are predators with a fondness for isopods, caddisfly larvae, and each other. The larvae will emerge and crawl under some streamside moss or rocks to pupate, emerging about three weeks later as these large monochrome flies.  Look for them in mid-May along clear, clean creeks and streams.

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