Scallop Shell Geometridae

Hydria undulata (Linnaeus, 1758)

Description: Wingspan 32-40mm. Forewings heavily marked with dark wavy cross-lines. Outer margin pale brown with a scalloped fringe. Hindwings similar to the forewings but paler.

Key Identification Features:

Sets:  male upperside

Flight Period: From the end of June to early August.

Status: Widely distributed but local, known from scattered sites mainly in southern counties. More frequently encountered in the fens and bogs of north Armagh than elsewhere including Brackagh Moss NNR, Selshion Moss and Annagarriff Wood NNR. In Down it has been taken at Lackan Bog and Belvoir Park. There are also recent records for Crom Estate, Garvary, Florencecourt and Reilly Wood NNR, Fermanagh.

Ecology: A rather scarce but distinctive moth, found in fens, damp woodland rides and clearings, particularly where willows are common. Adults appear sparingly at light and usually as single individuals. They become active at dusk and can be seen flying along woodland rides where they are easily netted. The larvae can be found from August to October on willow Salix spp. and Bilberry Vaccinium myrtillus. It overwinters as a pupa.

World Distribution: Northern and central Europe, also north America.

Bradley & Fletcher number: 1789 Agassiz number: 70.121

Additional information:

UK Moths account


 Thompson, R. S. & Nelson, B., 2003 (Oct 2). [In] The Butterflies and Moths of Northern Ireland