Description: Wingspan 50-64mm. The adult moth is green with white median cross lines on both wings. Mid-June to mid-August.

Irish Distribution: Widespread and frequently encountered in a variety of habitats particularly fens and cutover bogs in north Armagh and parts of Down.

Ecology: The largest of the Emeralds found in Northern Ireland inhabiting open woodland (especially birch), heaths and bogs. Adults are attracted to at light in moderate numbers but tend not to enter traps. Instead adults are often found in the vicinity resting among the vegetation. The larvae can be found from September to May of the following year on birch Betula spp. and occasionally Alder Alnus glutinosa. It overwinters as a larva attached to its foodplant.

Key Identification Features:

• Large size
• Wavy white median line on both wings
• Small white dots near the outer margin of both wings

Distribution Map from NBN: Geometra papilionaria at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Geometra papilionaria at iNaturalist World Species Observations database.