Ephemerella aurivillii Mayfly Nymph Pictures

Mayflies Caddisflies Stoneflies

Classification

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Ephemerellidae (Hendricksons, Sulphurs, PMDs, BWOs)

» Genus Ephemerella (Hendricksons, Sulphurs, PMDs)

» Species aurivillii

This is a puzzling one to identify and I'm not sure about the species. The maxillary palp (

The palp on the maxilla of an Ephemerella nymph (detached and photographed under a microscope) is highlighted in red here.

Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.) is present and segmented, and the maxillary canines are not strongly serrate laterally. I think it's Ephemerella, not Serratella. The ventral (Ventral: Toward or on the bottom.) lamellae of the gills on abdominal segment 6 have a clear median notch with a depth at least half the length of the lamellae, which points toward a couple of uncommon species (most likely Ephemerella alleni), but the abdominal tubercles (

A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled. They are especially large in this species.

Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.) and coloration don't fit that species. To add to the confusion, none of the above species are expected to emerge in the fall, as far as I know. I'm going to call this one Ephemerella aurivillii for now, but that's highly uncertain.

This mayfly was collected from the Foss River on September 10th, 2020 and added to Troutnut.com on September 19th, 2020.

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