West Wood Winchester, following up Helicodonta obvoluta

Some members may recall the Conchological Society field trip to Crab Wood and West Wood near Winchester (June 2009: see Mollusc World 22, 3-6). Being on my local patch, I have occasionally visited West Wood to see how the population of Helicodonta obvoluta is doing. On an earlier visit in May 2007, when the woodland floor was damp whilst the tree trunks were dry, I recorded twelve H. obvoluta and three Helicigona lapicida from between 20cm to 1.5m above ground level on the same beech trunk.

On another visit in July 2010, following two nights of persistent rain which came after thirteen weeks of very dry weather, I collected 15 shells of H. obvoluta from the remainder of the log pile examined during the field trip of 2009 (figure 1). The shells show a characteristic wide and deep umbilicus, flattened mouth and everted lip, calluses and some shells retaining hairs to adult stage (figure 2). I photographed two live specimens (figure 3) and one live specimen with an epiphragm (figure 4). A secreted epiphragm is normally associated with hibernation but perhaps in this case aestivation as a stress response to the preceding extremely dry conditions. This photo also shows the specimen’s flattened top and convex sides giving it a cheese-like appearance, hence the common name of Cheese Snail.

Moving into the wood I found several H. obvoluta at the damp base of trunks and also on the leaf litter surface up to 2m away from the trees and on fallen decaying branches. Over a period of two hours I recorded 57 live specimens. It is good to report that this population is doing well at its westernmost locality. In addition there were two live H. lapicida (figure 5) which were not seen on the 2009 field meeting.

My researches at Winchester College relating to the early life of the famous conchologist J. R. le B. (Jack) Tomlin, reveal that his early paper on local land and freshwater shells1 was read before the Winchester College Natural History Society at 8pm on Whit Monday May 29th 1882, by his younger brother Robert Ernest Tomlin. Where was the young Jack Tomlin? I like to think that maybe he had bunked off to Crab Wood on a more important mission in search of H.obvoluta and would not be back in time to read his paper: I wonder.

As a novice I would like to thank June Chatfield for suggesting that I might cultivate an interest in the molluscan world (particularly British land slugs and snails as there aren’t too many species to daunt the beginner) and for her continuing mentoring and encouragement. A thank you too to Graham Long for his encouragement and help.

References

1Tomlin, J R le B, 1882. Land and Freshwater Shells of Winchester Winchester College Natural History Society 6th Report pp.44-47, 1882

figure 1: Remains of log pile, West Wood near Winchester, 2010.

figure 2: H. obvoluta shells from the log pile site.

figure 3: Live H. obvoluta shells from the log pile site, note hairs on shell.

figure 4: H. obvoluta showing chalky white epiphragm.

figure 5: Live H. lapicida in West Wood.