Photo © Tim Norriss

September Thorn

Ennomos erosaria

Checklist Number
70.236 [B&F: 1915]

Verification
Record will normally be accepted but photo evidence may be required - check with CMR if not sure of identity

Classification

Family:Geometridae
Subfamily:Ennominae
Genus:Ennomos
Species:erosaria
Authority:([Denis & Schiffermüller], 1775)

Common in woodland, parks and gardens throughout much of England, spreading into Scotland, a species of conservation concern under the UK Biodiversity Action Plan. In Hampshire and on the Isle of Wight Common and widespread. Although the flight-time histogram shows a smooth curve of emergence, in most years there are two peaks, one in July and another, usually smaller, in September. Wingspan 38-42 mm. The most likely confusion species is August Thorn E. quercinaria, which has the antemedian fascia (the line nearest the base of the wing) acutely angled at the costa (almost straight in September Thorn). Larva feeds on Oak, Lime, Birch and Beech, over-wintering as an egg.

The abundance in each month is indicated as follows:

No records
Very occasional
Irregular
Uncommon
Off-peak, but not unusual
Off-peak, but not unusual
Main flight time
J F M A M J J A S O N D
Adult
Larval

Records by week (adult)

Records by week (larval)