Hampshire's newest slug, a lover of logs

Yesterday at the annual HBIC Recorders' Forum, local members of the Conchological Society brought a display stand including a live specimen of Limacus maculatus. This was found in the Lyndhurst area of the New Forest and represents a species new to Hampshire as of 2011.

Limacus maculatus

L. maculatus (previously in the genus Limax as is the case in many key British texts) is also known as the Irish Yellow (sometimes Green) Slug; it is widespread in Ireland (see map) where it is found commonly in towns and gardens as well as being associated with rotting wood in natural habitats (NMNI 2010). emerging at night to feed and climb. It is medium to large (70-130 mm long), yellowish to greenish and blotchy, with grey to blue-grey tentacles and colourless to yellow or orange slime. A common pattern variation has the darker mottling more fragmented such that the animal has a spotty appearance, similar to that of Limacus flavus (the Yellow Slug) which is similarly often given as genus Limax. These two species were previously considered to be the same (Cameron et al. 1983), though L. flavus is usually a paler yellowish colour and spotty, with a pale zone extending above the fringe of the foot whereas in L. maculatus there is dark pigmentation to the fringe of the foot, and the animal usually has larger dark blotches (though note the spotty variant mentioned above). As a rule of thumb, though care is needed as they are variable, L. maculatus is usually a darker and blotchier green while L. flavus is usually a paler and spottier yellow. See here for photographs of extended specimens showing the tentacles.

More widely, as well as Britain, it is known from France, the Canary Isles, Romania, Bulgaria, Ukraine, Russia, the Black Sea coast and the mountains of Transcaucasia (Turkey to Azerbaijan and NW Iran). Its full distribution is not known with certainty (Kerney, 1999), though it is considered to have been introduced by humans into the British Isles (as well as around Moscow and St. Petersburg), with its native range being the deciduous forests of the Crimea and Caucasus (Wiktor & Norris 1982, Sysoev & Schileyko 2009, Schütt 2010).

In Britain, most records of L. maculatus (see map) are from northern England, with a scattering elsewhere. While L. flavus is largely associated with humans (garden rubbish, damp cellars and outbuildings etc) with occasional records in woodland, L. maculatus is more strongly associated with woodlands, particularly beneath large logs, bark or in tree-holes where moist conditions are maintained (although it can be found in situations similar to those of L. flavus, as well as under stones in fields). The Hampshire specimens seemed to be associated particularly with large logs. Though found sometimes on rubbish, food put out for other animals, dead plants, or on lichens on walls and stones (Cook & Radford 1988, Schütt 2010), its strong association with large logs means that L. maculatus probably feeds on wood-decay fungi, suggesting that large fallen timber may provide both food and shelter. This diet (fungi, algae, lichens, dead plant material) is common among slugs and although many gardeners and vegetable growers dislike slugs, only a few species such as the common Field Slug Deroceras reticulatum actually feed on living higher plants (Kerney & Stubbs, 1980).

As a final note, the 'new to Hampshire' tag is a close one as it was found in Christchurch in 1884 (Kerney 1986) - though now in the county of Dorset, back then the town was in Hampshire...

Found L. maculatus in Britain? Let your local Biological Records Centre know...

References

Cameron, R.A.D., Eversham, B. & Jackson, N. (1983). A field key to the slugs of the British Isles. Field Studies 5: 807-824.
Cook, A. & Radford, D. J. (1988). The comparative ecology of four sympatric limacid slug species in Northern Ireland. Malacologia 28: 131-146.
Kerney, M. (1986). A 19th-century record of Limax maculatus in the British Isles. Conchologists' Newsletter 97: 361.
Kerney, M. (1999). Atlas of the Land and Freshwater Molluscs of Britain and Ireland. Harley, Colchester.
Kerney, M. & Stubbs, A. (1980). The Conservation of Snails, Slugs and Freshwater Mussels. NCC, Shrewsbury.
National Museums Northern Ireland (2010). MolluscIreland: Limacus maculatus (Kaleniczenko 1851) Irish Yellow Slug. [accessed 04/03/2012]
Schütt, H. (2010). Turkish Land Snails. Verlag Natur & Wissenschaft, Solingen.
Sysoev, A. & Schileyko, A. (2009). Land Snails and Slugs of Russia and Adjacent Countries. Pensoft, Sofia.
Wiktor, A. & Norris, A. (1982). The synonymy of Limax maculatus (Kaleniczenko, 1851) with notes on its European distribution. Joural of Concholology 31: 75-77.