Fróðskaparrit - 01.01.2006, Page 175

ÚTBREIÐSLA A V GRÁ UM UNDIR STEINI (ISOPODA: ONISCOIDEA) 173
IFØROYUM
Figure I. Oniscus asellus
niainly on rocky beaches under stones and
rocks. When disturbed it can either disap-
pear down between the rocks, or drop into
the water. Oniscus asellus and Porcellio
scaber are both about 10-15mm long. Both
are rather common in deciduous woods and
“hagi” (i.e. outfield); P scaber also occurs
in houses and e.g. birds’ nests. Trichoniscus
pusillus is the smallest species in the islands,
about 3-5mm long. It occurs in the samc
habitats as the other two terrestrial species.
The three first mentioned species have a nor-
nial reproduction, but T. pusillus can also
be parthenogenetic, implying that its ca-
Pacity for dispersal after immigration is
higher than for the others.
None of the isopods are pests; they are
niainly nocturnal and not usually seen dur-
ing daytime.
Woodlice are predominantly herbivorous
(Hopkin, 1991).
According to Poulsen et al. (1998) wood-
hce are eithercalled ‘grótlús’ or ‘grátt undir
steini’ in Faroese, but they are frequently re-
ferred to by different names.On the island
of Skúvoy they are referred to as ‘veggjalús’
(which is actually the bedbug, Cimex lectu-
larius) (pers.comm. Birgir Thomsen, Jóan-
nis Mikkelsen). Complicating matter fur-
ther, bristletails (Thysanura) are referred to
as ‘veggjalús’ in the village of Hvannasund
(pers. comm. Hans Jørgen Nysted).
Material and Methods
J-K. J. has systematically collected woodlice
since 2001, over a five year period, and has
been in contact with numerous people,
which have assisted with collecting on all
the islands, with the exception of Lítla
Dímun.
All collected specimen are preserved in
70% ethanol (a few are slide mounted ac-
cording to the method cmployed by Palma
(1978). The collected woodlice were iden-
tifíed by J-K. J. using a stereo loupe and the
key by Hopkin (1991).