Fróðskaparrit - 01.01.1998, Blaðsíða 278

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INSECT FAUNAS AT LANDNAM: A PALAEOENTOMOLOGICAL STUDY
AT TJØRNUVÍK; STREYMOY; FAROE ISLANDS
ing vegetation is also present, whilst the
flora provides hosts for three species of
weevil. Apion haematodes prefers sheep
sorrel, Rumex acetosella (agg.) (Morris
1990), which is not represented in the
pollen diagram, but is likely to have grown
on overgrazed bare areas of the surrounded
rock ledges. Notaris aethiops appears
polyphagous on a range of wetland grasses,
as well as Iris pseudacorus (Koch 1992),
and Ceutorhynchus contractus occurs on a
wide range of cruciferous plants.
The modern beetle fauna
Comparison between fossil and modern in-
sect faunas has serious taphonomic prob-
lems (cf. Buckland et al. 1991 b). Not only
is the fossil sample usually time-averaged
to an unknown extent, but it is also likely to
be dominated by those taxa immediate to
the sampled habitat and by mobile eury-
topic species. The problems have been dis-
cussed by Kenward (1976), who has advo-
cated a more statistical approach to the fos-
sil data, whilst recognising that the basis of
interpretation has to be remain a sound
knowledge of the modern habitat require-
ments of individual species. His methods
are difficult to apply on the Atlantic is-
lands, where faunal diversity is muted and
fossil assemblages usually small. Perry et
al. (1983) and Sadler (in Buckland et al.
1992) have used clustering techniques to
discern pattern in fossil assemblages from
Iceland, but direct comparison with modern
faunas, either pitfall trapped, with their
own inherent problems (c/. Adis 1971), or a
combination of this with searching and
sieved data, remains difficult. Both West
(1930) and Bengtson (1980; 1981) provide
detailed information on much of the fauna.
In August 1986, this work was supplement-
ed by a pit falling and search project around
Tjørnuvík to enable comparison with fossil
assemblages.
Pit fall traps were set in six different
habitats: i) close to the settlement in Rum-
ex-rich ungrazed meadow, ii) lush mown
grass meadow with R. acetosa, Rhinanthus
minor (agg.), and Ranunculus acris, iii) up-
per infield similar to ii, but less luxuriant,
iv) lower outfield of lightly grazed grass
heath, v) upland peat bog, and vi) along the
strandline at the head of the fjord, with
Honkenya peploides and Rumex crispus
The last habitat, with the strandline species
Cercyon littoralis and Omalium riparium is
not represented in the fossil record. The
modern faunas (Table 2) are dominated by
the carabids, Nebria salina, N. rufescens,
Patrobus septentrionis and Trechus ob
tusus, all of which are fairly catholic in the
Faroes. Neither species of Nebria is repre
sented in the fossil assemblage. N. salina
shows a preference for drier ground (e.g
Eyre and Luff 1990), and is likely to be a
post-landnám introduction. The species of
Calathus also prefer drier conditions
which may explain their absence from the
fossil assemblage. The infield sample (iii)
did, however, include a large number of the
small hydrophilid Megasternum boletoph
agum, found in dung and damp hayfields
(Bengtson 1981), which appears in the
landnám sample. Notiophilus biguttatus
occurs in large numbers in traps in the low-
er outfield areas, and the water beetles are
restricted to pools in upland bog and adja-