Mayfly Larva

Ephemera danica

The green drake mayfly larva (Ephemera danica) is a burrowing aquatic nymph reaching about 2.5 cm in length, found in rivers and streams across Europe. Its body is elongated and cylindrical with a pale yellowish-brown coloration, distinctive upward-pointing mandibular tusks used for digging, and feathery gills along the abdomen that wave rhythmically to maintain water flow for respiration. Mayfly nymphs are among the most sensitive freshwater invertebrates, requiring clean, well-oxygenated water, making them excellent bioindicators of water quality. They spend one to two years burrowing in sandy and silty stream beds, feeding on fine organic particles and algae. When conditions are right, nymphs rise to the surface en masse for their final metamorphosis, emerging as short-lived winged adults that famously live only one to three days, during which they mate and die. These mass emergences can involve millions of individuals and attract feeding frenzies from fish and birds. Freshwater divers may observe nymphs burrowing in the substrate or swimming with a distinctive undulating motion using their tail filaments.