Fróðskaparrit - 01.01.1996, Side 104

108
NOTES ON XESTIA ALPICOLA SSP. ATLANTICA NOV. ON THE FAROES
vain to the summer of 1996, when three
male specimens were caught on the island
of Kunoy and a further male was spotted in
the mountains of Viðoy, another of the
northern Faroe isles. The aim of the present
article has therefore been to discuss the
field observations of this highly interesting
moth species and to comment on the bio-
nomy and variation of the Faroe specimens.
Field observations on Xestia alpicola
on the Faroes
During the years 1990-1996 various efforts
were made in order to rediscover the
species. On August 12, 1990 the locality of
Eiðiskollur was visited in order to obtain an
overall impression of the habitat. The loca-
lity is a mountaineous area about 340 me-
tres above sea level. It consists of a rather
flat stony plateau sloping to the east and co-
vered with a semi-alpine vegetation which
includes one of the few known sites of
Dryas octopetala on the Faroes. In the area
there are many patches of Crowberry (Em-
petrum), a well-known food plant and pro-
tecting place for the hibemating larva of X.
alpicola: Despite fair weather the species
was not observed on that occasion. The fol-
lowing seasons the search included, in the
odd years, searches for the larvae under
Crowberry clumps on rocky substrates or
under moss on rocks in heathy areas on the
isles of Sandoy, Streymoy and Eysturoy, as
these methods have proved efficient in
Great Britain to obtain both young and full-
grown larvae during daytime, see e.g. Scor-
er (1913). In the even years 1992 and 1994
searches for the moth were made, partly by
examining isolated rocks in heath areas up
to 600 metres above sea level, or by at-
tempting to catch the male at dawn, where
it flies actively according to field observa-
tions in Arctic Finland (Mikkola and Jalas,
1977). These methods have also been used
by 1900-century British collectors in the
Scottish Highlands (Bretherton et al.,
1983). In Denmark stray specimens of X.
alpicola have been caught at mercury vapor
light in 1955 and 1965. It seemed therefore
possible that the moth might be obtained in
the automatic light traps which were opera-
ted as part of the general study of the isle of
Suðuroy at Akraberg (1990-1993) and
Trongisvágur (1994-96), on Stóra Dímun
(1994-96), Sandoy (1990-95), Nólsoy
(1993-96) and on Streymoy in Hoyvík near
Tórshavn (1990-95). Although heath areas
with the larval foodplants dominated at the
sites in Tórshavn and on Sandoy, no speci-
mens of X. alpicola were obtained in the
samples. In 1996 two light traps were
moved from Sandoy and Streymoy to the
northern islands Kunoy and Viðoy and
places close to areas with a semialpine ve-
getation. On Kunoy the trap was situated in
the village 100 metres above sea level with
about 500 metres to sightly grazed heath
areas, and about 1 km to the steep mountain
sides which surround the village area from
north to southeast. On Viðoy, the other trap
was installed on the eastern side of the is-
land, on a site 75 metres above sea level,
close to a moderately grazed heath area and
with about 1.5 km to the adjacent mountain
slopes to the south and west.
Both traps were controlled, usually at
weekly intervals, when the contents were
taken out and sent by post to Denmark for