Genus Nigronia - Dark Fishflies

Nigronia Banks, 1908

2 spp. total, both in our area(1)

20-30 mm

Key to spp. in(1) (both larvae and adults)

The easiest way to distinguish Nigronia fasciata from N. serricornis:

N. fasciata has a speckling of brown spots mostly on the base half of the white stripe on the forewing; lacking on N. serricornis.

Nigronia serricornis has a variable white band on the forewing, ranging from just a few white crossveins to a broad rectangular shape, there may be brown spots in the white costal area of the forewing but there typically will not be any brown spots in the rest of the white band, and the band will be opaque. The hindwing will have a strong to weak white band toward the apex and may have a weak white band toward the middle, and the rest of the hindwing will be a dark brown color. Will always have serrate antennae, deeper in males, shallower in females.

Nigronia fasciata has a consistent band on the forewing, it will always be broad and somewhat rectangular, it will typically have brown spots on the edge of the band closer to the base of the wing, and the band will be more translucent. The base of the hindwing will always be white, there will always be a strong white band toward the middle of the hindwing and there will usually be some white crossveins toward the apex of the hindwing. Females will have serrate antennae, males will have modified pectinate antennae. (Grant Schiermeyer's note here.

e. NA; both spp. widespread, but N. fasciata is absent from the upper Midwest and Canada(1)

Streams and nearby vegetation. N. fasciata tends to inhabit small streams with very good water quality(1)

in NC, May at lower elevations, May-July at higher elevations(2)

Emergence of adults may be synchronized. Adults are diurnal (seen flying near streams) and also nocturnal, so come to lights. Eggs are laid on the underside of vegetation overhanging a stream. Larvae are aquatic, predatory. Perhaps take three years to mature in more temperate areas, such as West Virginia. Pupation occurs in earthen cells on the edge of streams.