Rhithrogena germanica, known as the March brown mayfly in in the British Isle, is a species of mayfly that can be found throughout northern and central areas of Europe. Its range includes the River Tweed in England, Hesse in Germany, Denmark, Poland, and France. It was first described by Alfred Edwin Eaton, who studied a male specimen from the River Rhine.
Rhithrogena germanica begins its lifecycle in the larval stage, as a water dwelling naiad that is typically found in fast flowing, clean rivers. The naiads emerge from the water at the beginning of spring, between the months of Mach to April. At this stage, it is highly vulnerable to predation, but it is very fast at moulting and can jump from the water and fly within thirty seconds. This species, and other in the order Ephemeroptera, undergoes two adult transformation stages known as subimago and imago. The transformation between these two stages can take up to four days, longer than any other mayfly species. Its short and adults die after breeding.
Adult Rhithrogena germanica individuals, as well as subimagos, have two long tails and distinguishing dark spots on the legs. The species is thought to be declining across its range and Great Britain is known to be an important area for its preservation. The species is used by fly fishers as one of the most popular bait types to catch trout.
Image Caption: A female subimago of March Brown (Rhithrogena germanica) of family Heptageniidae. Credit: Richard Bartz/Wikipedia (CC BY-SA 2.5)