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- jaws like tusks
The mayfly is cream-coloured with dark areas on its back. It has clear wings with a few black spots. The tail threads are longer than the body and it has large gills along the back. The jaws are very large and protrude from the mouth like a pair of tusks.
Mayfly larvae prefer larger, clean waterways. They usually live in the watercourse stretches where the flow is good, and where the bottom consists of gravel and sand.
The larva lives buried in the bottom of the watercourse in a U-shaped tube. This provides good protection from being eaten by fish. It feeds on organic material from fungi, bacteria, algae and leaves that come drifting with the current.
Depending on the temperature and amount of food, the larva takes 1-3 years to develop into an adult mayfly. Like other mayflies, it is not fully developed when it comes out of the water. It has to shed another skin before it is an adult.
Seeking land
The newly hatched insects therefore seek land immediately, where they settle on the underside of leaves to complete their metamorphosis into adult insects.
Depending on the temperature and humidity it can take a few days before they shed their skin for the final time. After shedding their skin, they sit waiting for high, clear, dry and calm weather for their mating flight.
A fantastic sight
The mayflies mating flight is a fantastic sight. Thousands of males fly up to the top of the embankment's alder trees and let themselves fall with their wings positioned in a V, so they quietly fall a short distance before they fly upwards again.
After a short time they are visited by females who are willing to mate, who are immediately surrounded by suitors. After mating, the female usually seeks to return to vegetation until her eggs are matured. Then it flies off and lays eggs on the water surface.
Facts about the mayfly
Length: 25 mm
Wingspan: 45-60 mm
Bright green and yellow-green colours on the body. 
Common in larger watercourses on Fyn, Sealand and Jutland.