Main: (Geometridae / Ennominae)
70.235 [B&F: 1914] Dusky Thorn (Ennomos fuscantaria) (Haworth, 1809)


Common in woodland, hedgerows and gardens throughout much of England, a species of conservation concern under the UK Biodiversity Action Plan. In Hampshire and on the Isle of Wight although described as 'common and widespread' in the 2001 county history, this species was identified by a well-publicised long-term Rothamsted survey as having undergone a 98 decline between 1970 and 2005. Looking at the population graph shown below, it would be true to say that the position of Dusky Thorn mirrored the national picture towards the end of the 1990s, but since then, the population seems to have exploded, and it is now found at higher numbers than at any time in the past four decades.
The reason for this increase remains unclear, and although it may perhaps be at least partially explained by greater recording effort since it's plight was revealed, this cannot be the whole story. Wingspan 38-42 mm. The most likely confusion species is August Thorn E. quercinaria, which also often has discal third of forewing darker, but in Dusky Thorn the two median fasciae converge at the dorsum more noticeable than they do in August Thorn, and the postmedian fascia is smoother and less kinked towards the costa in Dusky Thorn. Larva feeds on Ash, over-wintering as an egg.

Flightime guide

Records Received By Year

% of total records
Max records: 637
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20

Percentage of Total Records

Total records
Max Percentage: 0.54979527
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20

Phenology - Adult Records

Max records: 812
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Distribution Map

Historical distribution at tetrad resolution
Click for density map

Record Density

As above but the larger the symbol, the greater the number of records
Click for distribution map

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