Ghost Slug Update, Spring 2010
Thanks to all 200 of you who have contributed so far! Since July 2008 we have had reports of sightings from all over the UK (and beyond) showing how far our message has travelled. As requested, many people sent photos or specimens that allowed us to verify the identity of their slugs, or brought them to the Museum here in Cardiff.
A definite pattern has emerged from the verified Ghost Slug records (see map). These are all from south-east Wales, with one from the English border at Hay-on-Wye and one from Knowle, Bristol. Although people in this part of Britain may have been more likely to respond to our appeal, we think this reflects the actual distribution of the species because our other responses came from so far and wide.
The map indicates the slug has already spread quite widely, but only within a small part of the UK. Why is this area so small? Perhaps because it arrived only recently, and is still on the move. The earliest verified sighting is from Brecon in 2004 ]. The slugs cannot have crawled all these miles by themselves, so must have been spread by man, probably in soil or compost. Alternatively, the area in which the slug has been found may simply be the region in which it best survives and breeds. The south-east Wales — Bristol region has a broadly similar climate and soils, which are evidently to its liking.
The verified Ghost Slug records have all been submitted to the Conchological Society of Great Britain and Ireland who record the distribution of all British and Irish molluscs.
Habitat and seasons
All the verified Ghost Slug records are from gardens, or urban areas adjacent to gardens. These are habitats in which many other alien species are found. Of course, they are also the places in which people are most likely to notice slugs. Live Ghost Slugs have been found at nearly all times of year (see graph). There is a peak in the warmer months that could reflect increased activity or numbers of slugs, but this is also when people spend more time in their gardens. It seems this species does not mind the cold! The latest observation proves that at least some Ghost Slugs have survived our coldest winter for 30 years; an adult was found in Cardiff at the beginning of March 2010.
Another pale slug to look out for
Many people confused the Ghost Slug with the Field Slug Deroceras reticulatum, included in our ID guide. This is a pale, herbivorous species common in gardens and lawns. A smaller number of people sent in pale specimens of the Worm Slug (Boettgerilla pallens). The name "Worm Slug" comes from the body shape; unlike the Ghost Slug, this species does not feed on earthworms. Like Field Slugs, Worm Slugs have eye spots and a breathing hole nearer the middle of the body. The breathing hole is in the saddle-shaped part of the slug called the mantle (see photo). The Ghost Slug is quite different; it has both the mantle and the breathing hole at the tail end of the body, and has no eye spots. The Worm Slug is thought to come from the Caucasus (the same part of the world as the Ghost Slug), and has spread very rapidly in Britain since the 1970s.
Are we still interested in Ghost Slug sightings?
Yes! We want to monitor any further spread of this species especially if found elsewhere in the UK or Europe. Contact details are on the ID guide. Remember that sightings must be verified with a specimen or photograph if they are to count.
Thanks once again to all those who have taken part.
Article Date: 6 June 2010