Spiny crawler mayflies

Overview

Ephemerellidae is a family of small to medium-sized mayflies known as spiny crawler mayflies. There are 148 Ephemerellidae species in 22 genera worldwide, 75 species in 14 genera in North America north of Mexico, and at least 21 species in 8 genera in Minnesota.

Spiny crawler mayflies occur throughout Europe and North America. They can be found in slow streams of all sizes and all substrates, and on lake shores and beaches that are exposed to waves.

The nymphs are poor swimmers. They are often found clinging to aquatic vegetation, moss, woody debris, stones, and gravel. They feed on dead plant material and on algae scraped from the substrate.

After emerging, the nymph transforms into a winged insect (subimago), then molts again into a mature adult (imago). Subimagos and imagos lack functional mouthparts and do not feed. They usually live no more than a few days.

Description

Adults are 3⁄16″ to ⅝″ (5 to 15 mm) in length. The body is slender. Most adults are olive green, yellowish, or brown.

The eyes are large. The antennae are short and bristle-like.

There are two pairs of wings. The forewings are large, membranous, and heavily veined. The hindwings are much smaller.

There are two or three long, slender tails at the end of the abdomen.

Nymphs have distinctive, plate-like gills on the sides of the abdomen. Unlike in all other mayfly families, Ephemerellidae nymphs do not have gills on the second abdominal segment. They have three cerci (tails) at the end of the abdomen.