White-spotted pinion moth  (Cosmia diffinis)

A UK Biodiversity Action Plan species.

The forewings of the White-spotted Pinion are brownish-red in colour (1). There are two roughly triangular spots on the outer edge (costa) of each wing, from which a whitish line extends to the inner edge (termen), that lightens towards the body of the moth (2). The caterpillar is pale green (3), with three whitish-yellow lines passing along the body, and a further yellowish line along each side of the body just above the legs. The head is dark brown or black, a feature that distinguishes this caterpillar from the others in this genus. When fully grown it measures 25-30mm in length (2).

In recent years, this moth has been regularly recorded in the UK from just one area, Huntingdonshire, where during the past five years it has been extending its range. However, during the past three years this moth has been recorded just over the border into Cambridgeshire where a couple of colonies now appear to be established. Furthermore, during 2002 this moth was recorded in Bedfordshire for the first time since 1985. Occasionally it is reported from other areas within its former range (2).

Historically, the species was widespread in central and southern England and areas of Wales, but it suffered a massive decline in the 1970s (4). In Europe it has been recorded in most countries with the exception of Ireland, Finland and Norway, but it is local and rare in many areas (4).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The caterpillars of this moth feed on the foliage of the English elm (Ulmus procera) and wych elm (U. glabra) (4) and have recently been found on small-leaved elm (U. minor minor) (2). The adults are found in woods, spinneys, field edges and shelterbelts where elm can be found. There is some evidence that the caterpillars prefer the side-shoots of mature trees, but the adult is also found in woods where there are no large mature trees (these having been lost to Dutch elm disease), so they undoubtedly feed on elm saplings as well (2).

Adults fly between the third week of July and the first week of September, with the second week of August being the height of the season (2).

The greatest threat facing the White-spotted Pinion is the risk of Dutch elm disease becoming rampant again, killing the remaining elm population. Other threats include the felling of trees and unsympathetic management (2).

This moth has been identified as a priority for conservation action under the UK Biodiversity Action Plan (UK BAP). The Species Action Plan resulting from this process aims to maintain all current populations, enhance populations by 2010 and restore the species to 3 sites in its former range, possibly using reintroductions. Some colonies occur within Sites of Special Scientific Interest (SSSIs). In addition, monitoring and research programmes have been proposed (4).

The UK Biodiversity Action Plan for this species is available at UK BAP.

There may be further information about this species available via the National Biodiversity Network Gateway.

View information on this species at the UNEP World Conservation Monitoring Centre.

Further reading on moths:
Leverton, R. (2001) Enjoying moths. Poyser, London.
Skinner, B (1998) Moths of the British Isles. Viking, London.