Scallop shell moth beds in at Inverewe

The scallop shell moth is widely distributed in southern Britain, although it is seldom numerous. In Scotland prior to 1970, this species had been recorded in only two areas: in Tayside, and near Edinburgh.

Between 1970 and 1999 there were no sightings north of Dumfries and Galloway. From 2000–2015 the records had advanced as far north on the mainland as Ardnamurchan in Argyllshire, but there were no records further north, east or west.

In 2016, the first record for Wester Ross was found in the wooded grounds of a Gairloch hotel. In 2020 a further four were recorded, one from the same hotel, and the other three from a Gairloch garden. Both sites have the damp woodland and scrub environment favoured by this species.

In 2021 five specimens were recorded, including the first for the Inverewe Estate where the available damp woodland was always going to attract this species if (as it seems) it is moving northwards. The estate’s diversity encourages a wide range of species favouring both cultivated and more natural habitats.

In the last 50 years, the overall abundance of moths in the UK has decreased by around 33%. This decline is reflected in many other insect species, and is a major cause for concern given their role in the natural systems we rely on for our wellbeing, such as pollination and vertebrate food chains.

Although moth abundance has decreased overall, there is a surprising increase in the distribution of some moth species. It is likely this is a reflection of a response to climate change – though not all species of moth may be able to adapt quickly enough. Of the 511 species studied 37% have expanded their range, 31% have remained stable and 32% have decreased. There is a well-documented northward movement for some species such as the lime hawk-moth and the orange footman and less well-known shifts for other species.

The varied and well-managed habitats of the Inverewe Estate will no doubt offer a haven for many range-changing moth species over the coming years and contribute to our understanding of these shifts.

Martin Hughes, Operations Manager for Inverewe and Corrieshalloch Gorge, said: ‘It’s fascinating to see new species discover the wonderful diverse habitat that is Inverewe. A huge thank you to Barry Blake for his hard work and diligence. Recording changes in the habitat at Inverewe is invaluable as we face the challenges of climate change.’

The Trust is supporting a local initiative to comparatively monitor moths within the gardens and on the wider estate. The resulting monthly data will show the succession of species through the seasons and will, it is hoped, highlight the ways in which a man-made environment shapes the moth population. Already it can be seen that the hardy early year species like hebrew character, clouded drab and powdered quaker are being joined by (and will soon be replaced by) later spring species such as water carpet, flame carpet and nut tree tussock.

Inverewe also comes up with the odd spectacular long-range migrant like the convolvulus hawkmoth, so it will be fascinating to see the arrivals as the year progresses.