Environmental Engineering Reference
In-Depth Information
FIG
145.
Berry Wood, near Knelston, a nature reserve managed by the Wildlife Trust. (Harold Grenfell)
INVERTEBRATES
The most important wooded common is Bishopston Valley, which is owned by the National Trust, al-
though woodland has also developed onother commons where grazing has ceased, such as Newton Cliffs
and Summerland Cliffs. Bishopston Valley, however, contains both ancient and recent secondary wood-
land and the underlying limestone has produced a rich flora that includes both small-leaved lime and
wild service tree. The damp and shady woodland floor with its carpet of rich leaf litter and rotting wood
provides a variety of habitats, which have a rich invertebrate fauna, including snails, millipedes, wood-
lice and ground beetles. The land winkle
Pomatias elegans
, the only winkle found on dry land, common
or two-toothed door snail
Cochlodina laminata
and tree snail
Balea perversa
are locally characteristic of
calcareouswoodlandsuchasthis.Thelandwinkleiseasilyrecognisedasitcarriesashelllid(operculum)
on the rear of its foot, while the frontal part of the head is prolonged into a snout. It moves by lifting one
side of its foot after the other, appearing to move forward on two feet. The tree snail is also unusual (per-
verse)becausethewhorlsonitsshellarecoiledanticlockwisewiththeapertureontheleft,ratherthanthe
more usual clockwise direction. The shell has a distinctive turret shape and is up to 1 centimetre tall.
Centipedes and millipedes, otherwise known as myriapods (literally many feet) are also common in
this habitat, and Gower is a particularly interesting area for these animals. At the northern end of Park
Woods near Llethrid, for example, there is an exceptional mean overwintering density of nearly 800 in-
dividual millipedes per square metre, 16 different species being present including a flat-back millipede
Brachydesmus superus
, a snake millipede
Ophyiulus pilosus
and a spotted snake millipede
Blaniulus gut-
tulatus.
Fivespeciesofcentipedehavealsobeenrecordedfromthesite,astonecentipede
Lithobius varie-
gatus
,
Geophilus insculptus
,
Strigamia acuminata
,
Brachygeophilus truncorum
and
Haplophilus subter-
raneus
. This latter species is one of the longest and broadest of the British 'geophilid' or ground-loving
