Large Dark Olive Mayfly Taken at Baron's Haugh on 1st May 2020 using Panasonic Lumix LX5 in macro mode. Large Dark Olive Mayfly.  Species: Order: Family: Local names: Baetis rhodani. Ephemeroptera. Baetidae. Larval Food: Body Length: Habitat: Flies/Found: Feature: They scrape algae from submerged stones or by collecting fine organic materials from the bed. 1 cm Around moving water. All year. Especially March - Autumn Once mated the female finds a partially submerged stone and folds her wings back over her body. She then crawls through the water surface and lays her eggs directly onto the submerged stone. She lays around 4500 eggs individually side by side so that they form a discrete patch of eggs on the stone.