Environmental Engineering Reference
In-Depth Information
FIG
146.
Waved carpet moth, a highly localised species which occurs in woods that have a long history of coppicing.
(Barry Stewart)
Twosmalltree-dwellingspeciesalsooftenoverlookedbythecasualobserverarethepurplehairstreak
Quercusia quercus
and whiteletter hairstreak
Satyrium w-album
butterflies. The purple hairstreak (Fig.
147) is a true woodland butterfly and the caterpillars, which are extremely well concealed, feed mainly
on oak buds and leaves. This close association is reflected in its scientific name, which uses the Latin
word
quercus
, meaning 'oak', twice. The numbers of adult butterflies vary greatly from year to year, but
it has been recorded from Oxwich, Nicholaston, Llethrid, Crawley and Park woods. The adults typically
fly high around the tree canopy and only rarely descend to paths and clearings, the females tending to
be more visible than the males. Purple hairstreaks are aggressive butterflies and will attack other insects
which fly into their territory, even wasps. They feed on the sugar-rich honeydew deposited by aphids on
ash and aspen leaves. The whiteletter hairstreak is a very local species and its caterpillars feed exclus-
ively on elms, which are fast disappearing due to Dutch elm disease. There are only a few records from
well-monitored sites such as Bishop's Wood and Oxwich. The adults spend a lot of time visiting bramble
and privet blossom for the nectar and the honeydew left by aphids. Elsewhere the species may be seen
wherever wych elm, or other regenerating elms, are found, but it is unlikely that more than one or two
individuals will be present. In contrast speckled wood
Pararge aegeria
is a common and widespread spe-
cies found in a variety of locations, not confined to woodland.
FIG
147.
Purple hairstreak butterfly in Llethrid Cwm. (Harold Grenfell)
BIRDS
The Gower woodlands support a wide diversity of breeding birds, as well as providing shelter and food
for migrants in spring and autumn. In particular Bishopston Valley is recognised as being especially im-
