Sialis the little known obscure aquatic insect!

Text & photos by Stefano D’Aluisi.

With the contribution of Fabrizio Fabbri.

In the fascinating world of aquatic insects, there are protagonists who often escape our attention. The Sialidae, commonly known as the “mud insect”.

The Sialis larvae have an active predatory attitude. They usually feed on other arthropods.

The name Muddy Bug comes from its habit of camouflaging itself in shelters built in the mud.

There are aquatic insects the fly angler knows and considers less than others. Accordingly, one of them is the Sialidae, commonly known as the mud insect. Specifically, this nickname comes from his attitude of using mud or sand shelters as a protective hiding place. Shelters that eventually become strategic lookout spots for hunting.

Sialis elegant figure and transparent wings often lead to confusion with common caddisflies. However, in addition to various similarities, there are also substantial differences that allow them to be distinguished. It is important to state Sialis and Caddis belong to a different order of insects. There are key distinctions identified between the two.

Sialis larva pupates in the mud.

Sialis larvae are found in many habitats, ranging from small springs to large rivers and from ponds to big lakes.

The Sialis has been imitated by fly dressers since ancient times. In fact, it is mainly known by the name of Alder fly.

Sialis, significantly present in certain habitats, constitute nutritious food for grayling and trout. Accordingly, Muddy bugs are interesting insects for the fly angler to imitate.

Adult insects of both species flutter in a similar manner. However, there are clear differences in the underwater larval phase. Trichopteran larvae adopt a variety of feeding strategies, such as particle filtration or debris-eating. Otherwise, the Sialis larvae are recognisable by their active predatory attitude.

Interesting to note that, one of the most extraordinary features of Sialis is its extended life cycle. The larvae can spend several years in water. As a result, this long life is truly surprising for an insect. In other words, this protracted larval stage contributes to their adaptability and importance in aquatic ecosystems.