Ephemera simulans (Brown Drake) Mayfly Nymph Pictures

Several of these pictures show larvae of the midge Epoicocladius (Diptera: Churonomidae: Orthocladiinae) attached to the gills of the nymph. This species is an obligate commensal that feeds on organic material that accumulates on hair tufts at the base of the gills. They are almost always present where burrowing mayflies are present in large numbers. Different species of Epoicocladius are found on Ephemera spp., Hexagenia spp., and Litobrancha sp.