A Common Resource - Gower - page 217

FIG 119. Map showing the distribution of marsh fritillary in West Glamorgan. Note the reliance on the wet and
marshy grassland in the northeast of the peninsula. (Barry Stewart)
The narrow-bordered bee hawk moth Hemaris tityus , a fast day-flying bumblebee mimic, has been
recordedfromanumberofcommons(Fig.120).Itslarvaefeedondevil's-bitscabious,buttheadultmoth
visits a variety of flower species for nectar. Once widespread in Britain, it appears to have retreated to
western areas of the country and it is classified as nationally scarce. The lowland area to the north of
the main ridge of Cefn Bryn is an important site for dragonflies and damselflies. The gravel-bottomed
streams support small populations of the nationally rare southern damselfly Coenagrion mercuriale (Fig.
121) and the scarce blue-tailed damselfly Ischnura pumilio (Fig. 122). They breed only in clear weedy
boggy streams and runnels in lowland heathland.
Other important insects found on the wetter parts of the commons include the black bog ant Formica
candida , which is found only on Rhossili Down, the valley bogs of the New Forest and the Dorset heaths
and is listed as an endangered species. A number of factors have been identified as causing its decline,
including excessive grazing pressure and trampling of nests, natural succession leading to an increase in
scrub,andgeneticisolation,inbreedingandlossofgenetic'fitness'.Furtherresearchisneededtoidentify
the precise habitat requirements and suitable management. The first Welsh record, reported as Formica
fusca ssp. picea ,isofaworkercollectedbyJ.W.Allen'inamarshyspot'atRhossiliin1913.Thisrecord
was subsequently questioned and considered to be probably a misidentification of Formica lemani . A
briefsearchofsuitablehabitatonRhossiliDownin1992bymembersoftheBees,Wasps&AntsRecord-
ing Scheme was unsuccessful, but a more extensive search in 1996 resulted in the species being found
again, at White Moor in the northeast of the Down. Certainly there is no reason now to doubt the first
Rhossili record. Subsequently, in 1997, transects across the site found 74 active nests, with an estimate of
between 84and 4,790nests across the entire area, a mean of2,420nests. This is the largest colony in Bri-