that a site does not have to be 'ancient' before a high density of large L. flavus anthills
might be recorded.
References
Curry, J. P. (1994) Grassland Invertebrates. Chapman & Hall.
Gibbons, B. (1995) Field Guide to Insects of Britain and Northern Europe. The
Crowood Press Ltd.
Rackham, O. (1986) The History of the Countryside. J. M. Dent & Sons Ltd.
Skinner, G J. and Allen, G W. (1996) Ants. Company of Biologists Ltd and the
Richmond Publishing Co. Ltd.
Molluscs of the River Stour
Theo Tamblyn 20 St Julian Grove, Colchester COl 2PZ
After much fruitful collecting in the River Colne after flooding in February 2009, I
decided to visit the nearby River Stour in the hope of finding freshwater molluscs
there. The result was astounding: 8 families of freshwater gastropods, 3 families of
bivalves and 7 families of terrestrial gastropods with an amazing 41 species in all,
well surpassing that of the Colne and indeed any rivers I have sampled at.
Two visits to the Stour, which marks the northernmost boundary between Essex and
Suffolk, were undertaken, on the 22nd and 28th of February. Both were in the sector
between Dedham and Manningtree. Specimens were collected by hand sampling, and
larger unionoid mussel shells from under the surface by using a hand net. Also, a
substrate sample was taken, dried and sorted to collect Pisidium mussels and small
gastropods.
Many species were found, mainly gastropods (19 spp.), although there were a fair
number of bivalves too with three families and ten species. Among the gastropods,
Planorbidae and Lymnaeidae were well represented, with excellent, large specimens
of Lymnaea auricularia and L. stagnalis. The commonest planorbid was definitely
Planorbis carinatus, with Planorbarius corneus close behind. Interestingly, the usu-
ally common Ansius vortex was very restricted, with only two specimens found. Two
vivipariid snails were found, one a possible Viviparus viviparus, the other a V. contectus.
The freshwater nerite, Theodoxus fluviatilis, was common, as were the two species of
valve snails, Valvata piscinalis and V. cristata. The Lake Limpet, Acroloxus lacustris,
and bladder snails, Physa sp., were uncommon, unlike the Hydrobiid, Bithynia
tentaculata. The other two species of hydrobiid were, however, uncommon.
Anodonta anatina was very common at one point, along with Unio pictorum and a
possible Unio tumidus. Sphaerium corneum was super-abundant everywhere, but
Musculium lacustre and Pisidium amnicum were few and far-between. Three smaller
Essex Field Club Newsletter No. 60, September 2009
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