Meet the Neighbors - Saw-Combed Dark Fishfly

I was walking the dog a few days ago by Dickinson Creek, a stream that runs next to our property. I noticed a large smoky colored fishfly fluttering along the edge of the water. It was conspicious in that it had large white patches on its wings. This suggested a visual component in their mating system.

After a few minutes it was apparent that there were several dozen of these large insects flying around. It looks A particularly interesting behaviour I have never seen before was that some insects fluttered up higher in the air, some into the overhanging treetops 40 or 50 feet up. Some of the high fliers flattened their wings into a fixed position and glided downward, until they reached the ground. Perhaps this was a display flight. Apparently an alternate French Name is Corydale papillon or Butterfly Fishfly.

I think the species is Nigronia serricornis.

According to a paper on post-glacial range expansion by He the Connecticut population of this species moved up the coast from North Carolina in a contiguous range expansion. Genetic diversity, as in many species of plants and animals thought to have expanded their range from the south after the Wisconsonian Glaciation, decreases from South to North. This second paper by Soltis et al. from 1996 titled Comparative phylogeography of unglaciated Eastern North America is a fascinating synthesis of many studies investigating how genetic differences in populations of the same species yield clues to population disperals after the last major glaciation.

BugGuide.net - a great reference, especially if you know the order or family your looking for.

Troutnut.com - Specializing in aquatic insects with fantastic photos.

Dr. Jeffrey Heilveil - Assistant Professor at SUNY Oneonta, has studied population dynamics of Nigronia serricornis.