Desmoulin's Whorl Snail Vertigo moulinsiana (Dupuy) in Essex
an advantage that would allow even individual snails to start small, fledgling populations. Thus,
there may be other as yet unknown populations in the same area.
At Parndon, the population would appear to be at its densest in two small areas of relatively low-
lying sedge bed, the western one possibly derived from a small pond since there was a good deal of
standing water at the time of the survey. These two sites are perhaps rather vulnerable to scrub
encroachment and management in the short term would probably be beneficial.
Summary
V. moulinsiana can still be found at its three traditional locations along the Essex/ Hertfordshire
border. It would appear to remain widespread at Sawbridgeworth Marsh, but more localised at
Thorley Flood Pound and Little Hallingbury Marsh.
In addition, this study has discovered a new locality for this species, at Parndon Mill, part of the
Stort Valley LNR in Harlow District. Here, the species appears to be quite widespread, although
most concentrated in two quite small areas close to the navigation.
This Parndon Mill site is now the second significant locality for V. moulinsiana in the modern
county of Essex.
References
BRATTON, J.H. (ed) (1991) British Red Data Books 3: Invertebrates other than insects, JNCC,
Peterborough.
KERNEY, M.P. (1999) Atlas of the land and freshwater molluscs of Britain and Ireland. Harley Books,
Colchester.
KILLEEN, IJ. (2003) Ecology of Desmoulin s Whorl snail. Conserving Natura 2000 Rivers Ecology Series
No. 6, English Nature, Peterborough.
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Essex Naturalist (New Series) 21 (2004)