Gloucestershire Naturalists' Society

Molluscs Report 2001 by David Long

The Conchological Society's Non-Marine Recorders' Report for 2000 (in press) adds 2 new vice-comital records for Gloucestershire. First, Ian Killeen found the minute and uncommon bivalve Pisidium tenuilineatum in the Coln at Coln St Aldwyn, v.c. 33, in the course of a survey using a very fine mesh scoop. Second, the Iberian slug Lehmannia valentiana was found in an allotment in 1999 at Westburyon-Trym by J M C Hutchinson. There is an earlier, 1993, record for Cheltenham (bark-strewn shrub bed outside a building) for v.c.33. L. valentiana looks superficially like the Tree slug Lehmannia marginata but is a ground dweller. It was originally introduced into greenhouses in Britain and Ireland, but since a first record in 1981 has increasingly been found in the open, mainly in such sites as gardens.

In July a Conchological Society field meeting visited Purton Timber ponds, looked at the adjacent Gloucester-Sharpness Canal, and then went on to Walmore Common. At Purton we did not re-find the introduced N. American bivalve Musculium transversum but the ponds produced two snail species typical of "good" situations Planorbis carinatus and Bithynia leachi. The latter was also found in the canal which produced such typical canal and river species as the River nerite, Theodoxus fluviatilis, and the Common river snail, Viviparus viviparus, along with the Zebra mussel, Dreissena polymorpha, introduced in the nineteenth century, which can be a serious pest. No mollusc recording had been done on Walmore Common since 1969; in 2001 15 freshwater species were found, one of which, the Moss bladder snail, Aplexa hypnorum, has few known sites in Gloucestershire.

With David Haigh's help in return for any spiders I find, I have been doing the annual Gloucestershire Wildlife Trust mollusc survey. In 2001 it was Siccaridge Wood, Sapperton, which was known from past records to have a good mollusc fauna. Since mid-May we have visited nearly all the 100 x 100m grid squares in the wood, and with Keith Alexander's October record of the Ash-black slug, Limax cinereoniger, all but one of the ancient woodland indicator species previously known, including the RDB3 Mountain bullin, Ena montana (good population), have been re-found, and one addition, Aciculd fisca, has turned up, perhaps unsurprisingly. The exception is the very local glass snail, Phenacolimax major, with old records from 1968-86, best searched for from late autumn through to May, where this year's search was delayed by Foot and Mouth Disease restrictions.

Many thanks to David Scott-Langley for further records of Hygromia cinctella and other molluscs.

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