Every June, The Tisza River in Hungary Blooms With Millions of Mayflies

Every summer, tourists swarm to the River Tisza to witness the ‘Tisza blooming,’ the spectacular mating of mayflies, when millions of the aquatic insect’s larvae usually hatch and mature in a single week.

tisza mayfly blooming 3 — Image credit: Hortobágy National Park Directorate

The mating of mayflies is unique not only in Hungary, but now also in the world. Even Aristotle mentioned these short-lived insects, famous for their beautiful mass mating dance, and called them Ephemeron (living but for a day). The Hungarian equivalent, ’tiszavirág’ is also used to denote a short life.

The mayfly (Palingenia longicauda), also called the long-tailed mayfly and giant mayfly since it is the largest mayfly species in Europe, measures 12 cm (4.7 in) from head to tail. Female Tisza mayflies usually lay about 7-8000 eggs on the surface of the water, and their development lasts for 3 years. The end of this period triggers their spectacular mating, the ‘Tisza blooming’, which is most undisturbed in warm, windless weather.

tisza mayfly blooming 5 — Photo: Andor Derzsi Elekes

Males begin their brief adult life (ranging from a few hours to half a day) after flying ashore. A little later the females appear, caring only about finding their partner, and not even feeding.

During the most spectacular part of the mayfly mass-mating, millions of specimens fly over the river Tisza, creating a beautiful dance (see video below). The amazing spectacle occurs in the late afternoon and evening, usually between 18-21 hours.

tisza mayfly blooming 2 — Photo: Mirjana Rankov

Apart from being spectacular, the Tisza blooming also has important ecological significance, as the mayflies feed many species of fish, birds, and frogs.

In Western Europe, the mayfly went extinct at the beginning of the 20th century, and their numbers also went down significantly in Central Europe in recent decades. Beside climate change, river regulations and alterations, plastic bank protection of riverbanks, and river pollution have also largely contributed to the drastic reduction in the number of these insects. Today, the river Tisza in Hungary is the only place where you can find them in mass numbers.