W19 Flowing water,
an interesting habitat - Turn stones in Lauter river
a morning with a children group of Eichberg Primary School Lauterbach
at 19.06. 2008
1. Investigation of Lauter a small stream close to the school
Flowing water is the habitat of
different animals. Probably you will only find small ones:
Mayflies
are born in the Lauter from eggs. The females have only a short life. After a
very short time ashore they return to the water: Underside a stone they
fix hundreds of small eggs. After months a baby mayfly (called larva)
is hatching from each egg. In spite of their small size they resemble mayflies.
During their whole underwater life the larvae are distinctive in that they breath through 7 pairs
of gills at both sides of their belly (abdomen). 3 tails can be seen at its
end. Like other insects
they have 6 legs at their breast
(thorax) and two big eyes aside
their head. The larvae feed on
algae and grow quickly. After a short time their hard skin is too small for them.
Below the outer skin a soft skin is growing. The outer skin cracks and the larva
leaves it. 
Now
it is growing again and soon the second skin is also too small. It bursts as a
third soft skin has been formed. When the larva has reached its final size it
has to leave the water and the female or male mayfly is hatching.
Larvae (of one species in the Lauter) can be seen on the first photo and on the sketch at ist side: This larva is
flat and streamlined. Therefore it cannot be drifted off even when the Lauter
is in flood.
In the Lauter you will find another species of mayflies
that have not this streamlined shape.
In the Lauter you will also find larvae of caddisflies. Most of them
are underwater architects: They build a house from small stones or other
materials (left 
photo). Another species also present
inn the Lauter does i the Lauter does not have such
a house (right ): Like mayfly larvae they a
head with eyes, a thorax with 3 pairs of legs and an abdomen with 7 pairs of gills.
Larvae of caddisflies hatching from eggs are also growing, changing their skin.
When they have reached their final size they close their house or build one to
transform in a male or a female caddisfly that leaves the water. They resemble
small butterflies. In
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Stonefly larva / its
last skin / male /
female with male / with parcel of eggs
Stoneflies
have their name because they live under stones escaping light and current.
The
species on the photos lives in the Lauter close to the fountain. In this habitat the water is cold all the
year. So it can dissolve more air than the water close to your school. These
larvae have no gills. So they suffer from lack of air (click
for video). Before transforming into a male (small, only stumps of wings)
or a female (Photo 3 and 4) they have a length of 2 - 3 cm. The stonefly larvae
you might find are much smaller.
2.
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back go
on first
publication: 18.06.2008 last modification: 21.12.2008