The Butterbur Hydraecia petasitis
Doubleday, 1847Wingspan 44-50 mm.
The larvae of this moth feed from April to early July in the stem, then in the roots of Butterbur (Petasites hybridus). The larvae can be found in late May and early June by cutting through the stems about 10cm below the leaf. If a brown line descends down the inner stem it usually suggests the presence of the larva. If found at this stage, the possibly cannabilistic larvae should be reared (separately) on potted foodplant.
The adults emerge in August and early September, and as easily overlooked, may be locally common in marshy places and river-sides where its foodplant can be found.
The moth occurs throughout England, Wales and southern Scotland.
The adults may be confused with the similarly marked Rosy Rustic, but can be separated by its larger size, broader, darker forewings and hindwings, and the absence of a pinkish colour.