Species of the Month: Green Cellar Slug Limacus maculatusis (September 2024)

A familiar species of gardens, compost heaps and woodland debris it may come as a surprise that the Green Cellar Slug Limacus maculatusis is a non-native species. There is a very similar closely related species called the Yellow Cellar Slug Limacus flavus which, whilst it was here first, is also a non-native. Both are often found around human habitation.

This is a tale of a war of slugs, a slow clash of invaders vying for supremacy of the British Isles. The Yellow Cellar Slug was first recorded in 1685 and subsequently spread throughout the British mainland unopposed, adapting well to human habitats. In the 1970’s a new species was discovered in Ireland – the Green Cellar Slug. Since that discovery the Green Cellar Slug has been on a conquest and has now spread throughout the British Isles. Now the initial invader, the Yellow Cellar Slug, is quite uncommon and has largely been supplanted by the Green Cellar Slug.

Whilst both species are similar in appearance (and it should be noted they can also hybridise) there are a few key differences. The Yellow Cellar Slug is warmer in colour and overall is usually paler. The body is more slender and typically has a central pale stripe that runs along the keel down to the tail. It is likely that the Yellow Cellar Slug is overlooked locally due to these subtle differences, but we know it is still present as it has been recorded sporadically.

As true omnivores, these species will eat anything vaguely edible, although live plants do not form as large a part of their diets as other slug species. Delicacies they have been recorded eating include wallpaper paste, faeces, mould, food scraps and carcasses. Truly the living dustbins of suburbia.

September is a peak time to find slugs due to the wet conditions and abundance of decaying matter (slug food). Slugs are a much-overlooked group and any records of these or other species would be much appreciated. Certainly, we would be keen to see how the saga of the slug wars is playing out here in Ayrshire and Dumfries & Galloway. A good photograph should accompany any records of these species so that their identity can be confirmed.

Malcolm Haddow

SWSEIC Support Officer