Phylum Arthropoda (Arthropods) ➔ Subphylum Hexapoda (Hexapods) ➔ Class Insecta (Insects) ➔ Order Megaloptera (Alderflies, dobsonflies, fishflies) ➔ Family Sialidae (Alderflies)
Sialis sp. Latreille, 1802
Schlammfliege
Distribution:
Widespread in Central Europe.Habitat:
In the riparian vegetation of flowing or stagnant waters.The most common species in Germany Sialis lutaria can be found mainly near stagnant waters, and more rarely also near slow-flowing waters. The Sialis fuliginosa, which is quite common in mountainous areas, prefers fast-flowing streams. The rare Sialis nigripes usually lives on the banks of larger rivers.
Description:
The dark brown appearing alderflies of the genus Sialis have brownish tinted, translucent wings with distinct dark veins. The wings are laid together like a roof in the resting position. The wingspan is about 23 - 35 mm. The males are on average smaller than the females.The adults of the Central European Sialis-species can only be distinguished from each other by genital morphology.
Biology:
The diurnal adult alderflies can be found near water from the end of April or May to August. They rarely fly and often rest in the riparian vegetation.After mating, the females start to lay eggs. The eggs are usually laid in larger groups close to each other on the leaves of the shore vegetation rising above the water surface. After hatching, the young larvae fall into the water. At first they swim freely around and later colonize the muddy bottom of the water. They are predators feeding on insect larvae, worms and snails. At the end of the usually two-year development, in which 10 larval stages are passed through, the fully grown larvae leave the water and look for a suitable pupation place. They dig themselves into the soil and shed their last larval skin. After a pupal period of 2 weeks the new generation hatches. In contrast to the larvae, the adults, which have rarely been observed while eating on pollen and nectar, live only a few days up to a little more than 2 weeks.
Note:
The alderflies shown here were all found in the shore area of standing waters and probably belong to the most common species Sialis lutaria.The small alderfly of 2019 had a total length (measured from head to wing tip) of 12 mm. Both the fore wing length and the body length were about 10 mm.
References, further reading, links:
- Heiko Bellmann: Der KOSMOS Insektenführer, Franckh-Kosmos Verlags-GmbH & Co. KG, ISBN 978-3-440-15528-8.