Conservation report
This month, Mark Tunmore shines the spotlight on the ‘Holy Grail’ of British moth species.
Clifden nonpareil moth
Why are naturalists excited about this migrant moth?
It is a spectacular species with quite a mythical status amongst entomologists in the UK. Compared to other moth species here, it is huge, with a wingspan that can reach 11cm and blue underwings – a colour that is quite rare to see on a moth.
Why is it difficult to see one?
The blue underwing, as it also known, became extinct as a breeding species in the UK the 1960s. One famous site, Orlestone Forest in Kent, lost the species due to the post-war changes in forestry and the clearing of aspen and poplar (the caterpillar’s main foodplants) and other trees. For decades afterwards, it was only recorded as a scarce immigrant moth from Europe, with less than one sighting a year.
What has changed?
Some of these immigrant moths have re-established breeding colonies in southern England in the last decade or so, and records from 2018 suggest that it is spreading into Wales and the Midlands. There is some very interesting data from Warwickshire this year that demonstrates the species’ increased range.
How do you know the moth is breeding in the UK again?
Caterpillars have been found in Sussex, part of the species’ former UK range, but only a few so far, because they are very difficult to find – they feed nocturnally and in the tree canopy. One thing that tells us it is resident again is repeated occurence over several seasons at recolonised sites, and its appearance in multiple numbers at some of those same sites, many inland. This is not the pattern of a migrant species.
Can anything be done to improve its breeding success?
I suspect from the trend we are seeing that it doesn’t actually need much help from us. However, planting their caterpillar foodplants may help, as would retaining woodland and looking after trees, which we should be doing anyway. With so many widespread moth species in decline it is nice to have a good news story for once about an enigmatic moth that is doing well. Megan Shersby
MARK TUNMORE is editor of Atropos and founder of Moth Night.
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