L'habitat e la biologia di Helicopsyche sperata Me. L. in Toscana

Summary

After a chorologic reference to the genus Helicopsyche Hag. (Trichoptera-Sericostomatidae), there follow a few brief historical notes non the European species, and in particular on the H. sperata Mc.L., founded in Toscana after a bibliografical silence lasting from the last century.

Clarified the springal habitat of the species in an survey carried out on the 136 sourcse between 1954 and 1959 years, the Authors have produce an analytical balance of the surrounding areas wich woidd seem to condition the colonization of the sources on the part of this tricopter. The elements considered are as follow, the form of the spring bed, the nature of the soil, the rock structure, the type of bottom, the vegetation, the altitude, the inclination, the direction, the classification Thienemann-Steinmann, the water quantity, the pH, the oxygen, the hardness, the presence of iron and the temperature.

It has been possible to establish that the H. sperata prefers to inhabit springs of an exiguous water mass, with clear waters running softly in veils over a pebbly, stony or dead-leave covered bed.

The sources with H. sperata appear to be all within a few metres above sea level (Island of Elba) and a thousand metres of altitude (Appcnnino Pistoiese). Among the terms wich accompany H. sperata in the composition of the biocoenosis there are representatives of the hygropetric, eufonticol, subfonticol, torrentieol and bryofil exponents.

The eggs of the H. sperata are laid on blades of grass or half submerged bodies. In the first stage of coleobiosis the caddy is right, only later does it curve spirally.

It is nymph in June, and the flying period lasts from July to about the middle of September.

The little swarms flittering around the sources are formed in the vast majority of males.