Clancy Tucker's Blog: 21 November 2014

21 November 2014 - TISZA MAYFLIES

TISZA MAYFLIES

G'day folks,

Welcome to something different.

Between the end of spring and the beginning of a new summer, the Tisza River in Hungary is host to one of the most incredible natural phenomena, as millions of long tailed mayflies form huge masses and rise from the water, flutter and dance above the surface, mate, flutter and perish, all in a few hours.

This amazing event may last for 3-4 days, and is commonly known as the "Blooming of the Tisza". The Tisza mayfly was named after the river it is found in, and is the largest species of mayfly in Europe. Their average length is about 12 cm (4.7 inches) from head to long tail. However, most of their lives - 3 years - they spend as larva living in the mud at the bottom of the river. After hatching, they are pressed for time; the males have only hours to find females and mate with them before they die.

As a result, the males swarm and dance above the river, trying to mate with the females on the surface. After mating, the females will fly upstream (because their eggs will drift with the current of the river) and deposit their eggs along the way. The eggs will drift and after 45 days, hatch into the larva. The larva then create tunnels in the mud, creating crude and densely populated colonies. 3 years later, the cycle begins anew.

With the males having barely 3 hours to carry out the biggest mission of their lives and all of the hatching happening at once, the sight of the synchronized dancing of these millions of insects is astounding. As you will see in the photos below, their numbers are so great that at times it is impossible to drive on nearby bridges and roads! Also, after mating, most of these mayflies die, which means huge piles of them need to be cleared off the roads. They are harmless to people and so many gather to watch this incredible display - a mass mating dance.

From a biological point of view, the advantages of this huge, synchronized hatch are obvious: as insects can only mate in their adult stage, by synchronizing the hatch, the chance of finding a partner is maximized, which is very important for species with such a short adult life stage. Furthermore, predators like bats or birds are surprised by this sudden appearance of clouds of prey, and so can hunt only a small fraction of the population.