Hydraecia petasitis Doubleday, 1847

Host plants:
The caterpillar lives monophagous in Petasites hybridus.

Habitat:
Hydraecia petasitis inhabits the shoreline of rivers, especially small to medium, only little straightened streams in the forest or in the company of a gallery woodland.

Life cycle:
The eggs overwinter. The young caterpillars can be found easily at flowering time and early maturity of the fruit stands (April to mid-May) by paying attention to wilted or withered shoot tips. When you cut the shoots at ground level and rip them open, you come across the larva in the tube. However, there is also an other small moth (Microlepidoptera), which produces a similar feeding pattern (observed in the Swiss Grisons).

The older caterpillars live first in the petioles and finally in the rhizome/tuber of the plant. Pupation usually takes place in July or August in a burrow. The moths fly from July to September or early October, with a maximum in late August and early September.

Endangerment: endangered

Endangerment factors:
Hydraecia petasitis is probably more widespread than previously thought. In studies of two rivers in Baden-Württemberg with Petasites in April/early May 2010 (one in Schwäbisch Gmünd, one near Aichstetten in Upper Swabia) I recorded Hydraecia petasitis each immediately.

However, Hydraecia petasitis has lost many habitats in recent decades by straightening of rivers, shadowing by spruce monocultures, overbuilding and other destructions of the sites, so it has become rare in many regions.

Remarks:
Hydraecia petasitis is fairly widespread in Central Europe from England and eastern France to the north to southern Sweden, south to Italy and in Eastern Europe (from the Baltic states to Bulgaria). Further east it is very local in the northern part of Asia, but where it should presumably be a little more widespread than currently known.