july 2007

The brief, lusty life of the mayflies from River Tisza

Photographs by Milan Radisics


Three year in hibernation for few hours of life

Tisza’s Palingenia longicauda belongs to the ancient group of mayflies (winged insects, members of the insect order Ephemeroptera), living on the Earth since centuries. The Hungarian species is singular; Europe’s largest mayfly measuring up to 12 centimeters.

The miracle of perfect biological timing occurs every year in the middle of June, but the exact date is not known, since the positive coincidence of adequate Moon phase, water quality and temperature determine the time of swarming. The process begins at the Lower-Tisza and repeats every day at sunset between 6 and 8 o'clock p.m. for two weeks, drawing slowly to the source.

Having spent three years in the muddied bottom of the river the larvae break for the surface where the females molt once and the males shed twice. Once reaching the face of the water they briefly turn into so-called subadults. A few minutes later they head for the river bank transforming into fully-fledged adults.

Mayfly larva colonies are present mostly at clayey riverbed areas, where usually three generations live together. During the mating period, mayflies cover the river surface for 2-3 hours and finding each other, they begin to reproduce. This is an act when more dozen of males simultaneously go after a single female, while they together form a flower of wings – a flower of Tisza – this is why this phenomenon is named “Blooming of Tisza”.

After reproduction, the males die. The females begin their bridal-flight. The nymphs lay eggs on the surface. They are able to fly 2-3 kilometers against the watercourse to place their eggs, which are driven back with perfect timing by Tisza to the same place where their parents first saw the light of day. The eggs drift to the bottom of the river, hatch into larvae and dig themselves to the river bed 7-8 mm deep, where they develop three years long.

Males have only a few hours to find females and mate before both sexes die.


Photographs by Milan Radisics

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