Fróðskaparrit - 01.01.1996, Side 107

NOTES ON XESTIA ALPICOLA SSP. ATLANTICA NOV. ON THE FAROES
111
tions of these boreal species which have or
are thought to have two fixed obligatory di-
apauses in their larval stage. This feature
characterizes the two boreal Scandinavian
Xestia-species alpicola and speciosa
(Sandberg, 1883). The stable alternate-year
cycle may be due to the regulative effect of
parasites such as Braconid wasps with an
annual cycle. This cycle may constitute an
effective barrier prohibiting moths with a
»wrong« two-year cycle to increase in the
same area. In this way a very stable two
year cycle can be achieved. The presence of
specimens in an intervening year may
therefore either be the result of immigration
from neighboring populations with a diffe-
rent year cycle or originate from those few
larvae which enter into a third hibernation.
This feature in the larval biology of X. alpi-
cola was already observed in the last centu-
ry in Arctic Norway (Sandberg, 1883).
The variation ofthe Faroe
Xestia alpicola Zett.
The four Faroe specimens are all of a uni-
form appearance which differs from the
typical ssp. alpicola in northern Fenno-
scandia and ssp. alpina from northem
Great Britain. Obviously they represent an
isolated and hitherto unrecognized local
subspecies.
Xestia alpicola atlantica subspecies
nova: Male wing span ranges from 35.7 to
37.0 mm, mean 36.3 mm. Forewing ground
colour uniform dark slate grey with a faint
purplish tint, especially along the inner bor-
ders of the postmedian line and the reni-
form stigma. Orbicular stigma pale grey
and conspicuous, reniform stigma darker
and surrounded by a distinct black line.
Claviform stigma black and distinct. Ante-
median and postmedian lines black and
without contrasting pale bordering. All
males have extended black markings in
basal field and well-developed interneural
chevrons along termen. Hindwing colour
brownish grey, distally darker with a faint
discal spot. Female wing span 34.6 mm.
Forewing color grey with a contrasting me-
dian field with traces of red brown scales
located as in the male. Orbicular and reni-
form stigma well-developed, bright grey
and coalescent. Line markings as in male.
Hindwings light brownish grey as in the
male. The wing colours of the female speci-
men have faded considerable due to contin-
uous exposure to artificial light in Tórshavn
until 1990. Two of the male specimens and
the female are shown on Plate 1 together
with specimens of ssp. alpicola and ssp.
alpina.
The type material of the female is kept in
the Museum of Natural History in Tórs-
havn and the males in the Museum of Natu-
ral History, Aarhus.
Comments. The appearance of the ssp.
atlantica covers elements both from ssp.
alpicola and ssp. alpina. Thus all Faroe
males are larger than the female - a feature
which distinguish ssp. alpicola from the
Southern Scandinavian race, ssp. iveni
Hiiber, 1870 (Mikkola et al„ 1994). Con-
trary to the Faroe specimens ssp. alpicola is
characterized by its light brownish grey
forewing color and the pale bordering of
the median line pattem, and almost no red-
dish coloring, see e.g. Nordstrom and
Wahlgren (1941) and plate VIII in Mikkola