Species Account

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Summary Data

Season (Adult / Immature):

National Status: Common

Local Status: Uncommon and fairly widespread resident.

Local Record: Grade 1   See here for explanation

Flight time: One generation, Jul-Oct.

Forewing: 17-21mm.

Foodplant: Ash.

Regional breakdown:

Year first recorded19041953188318831978
Year last recorded20142014201420142014
Number of records346449510781113
Number of individuals3017026811607166
Unique positions84509911819
Unique locations845210311618
Adult records327440497755113
Immature records40000

For the county, we have a total of 2199 records from 373 sites. First recorded in 1883.


1914 Dusky Thorn 08
© Nancy Stedman
1914 Dusky Thorn 07
© John Gardner
1914 Dusky Thorn 06
© John Gardner
1914 Dusky Thorn 05
© Damian Money
1914 Dusky Thorn 04
© Nick Lawman
1914 Dusky Thorn 03
© Andy Nunn
1914 Dusky Thorn 02
© Ian Andrews
1914 Dusky Thorn 01
© Ian Andrews

Species Account

Sutton & Beaumont, 1989: Widely distributed and sometimes locally common in an area for a few years. Many populations seem to either be transitory or subject to large variation in numbers.

2012 (CHF): In the Rothamsted data this species had declined by 98% between 1968 and 2002 making it the moth with the biggest drop in numbers. This seems to have been most marked in the south and numbers in Yorkshire were doing fairly well until 2009 when records dropped by a significant amount. This species may be prone to major fluctuations and it is interesting that Porritt regarded it as "generally scarce" in 1883 which he altered to "local but not uncommon" in 1907. Records are currently spread all across the county with the exception of the far west.

See background to species accounts.  Index of Vernacular names - Search - Random Species