Jökull - 01.12.1986, Síða 53

28-,
24-
o -
X 20-
o
ó 16-
2
Q) > 12-
o
o
E o 8-
o _
4-
0 L
0
PRE-LANDNAM
4 8 12 16 20
POST-LANDNAM
24 ' 28 1 32
No. of samples
Fig- 7. Ketilsstadir: cumulative number of insect taxa
plotted against the number of samples. — Mynd 7.
Graf sem sýnir tegundafjölda (safntölu) skordýra sem
fall af sýnatöku.
As well as the dung beetle, the greater part of the
msect fauna associated with stored hay must have
been introduced by man. At Holt (Sveinbjarnardóttir,
1983), much of the fauna has been found in deposits
dating to shortly after Landnám, but at Ketilsstadir,
probably because of the greater distance to an
occupied farm, only one individual belonging to this
group has been recorded. A single elytron of Lathri-
dius sp. was found in sample KE/Supp., from the
corner of a peat cutting infilled with ash from the
— 1357 eruption of Katla (fig. 4). Whilst Larsson and
Gigja (1959) list only L. minutus from Iceland, recent
work on the genus (Tozer, 1973) has shown that this
taxon consists of three species and specimens, taken
by Drugmore (1981), from barns in Eyjafjallasveit,
have been determined by Tozer (pers.comm.) as L.
minutus L. and L. anthracinus Mannh. Since it is
possible that the third species, L. pseudominutus
Strand, may eventually be identified amongst Icelan-
dic material, the identification of the fossil has to be
left at L. (minutus) group. All three species are
markedly synanthropous in the northern parts of their
distribution, being common in the artificially warm
environment of stored, mouldy hay, where they feed
on fungi. They are, however, effective fliers, dispers-
mg out into the hayfields on warm days in summer
(Dugmore, 1981), and the presence of an individual in
the Ketilsstadir peat cutting is not surprising.
Several other, less synanthropous taxa are only
recorded from post-Landnám deposits (table 2) but
their significance can only be assessed after the study
of several comparative sites (cf. Buckland et al.,
1986), although some clearly reflect habitat variation
on and around the bog. The opening up of the bog
surface by peat cutting would have provided habitat
for such species as Lesteva longoelytrata and several
taxa must reflect changes in the immediate vicinity of
the bog. It is probable that the poorly vegetated slopes
of Geitafjall today are anthropogenic, a result of over-
grazing by sheep. Some beetles, in particular, Amara
quenseli and Byrrhus fasciatus, would have found an
expansion of suitable habitats as a result of this loss of
soil cover. Others, like the forest element represented
by Strophosomus melanogrammus, have seen a pro-
gressive impoverishment of their biotope. Similarly,
animals of wet meadowland and Sphagnum bog, like
Lathrobium brunnipes and Hydraena britteni may
also have seen a decline in their available habitats,
particularly as modern drainage techniques have
come to be more generally applied. More quantitative
data on Coleopteran assemblages is, however, re-
quired before the impact of such changes can be fully
understood.
DISCUSSION
A major problem in the more detailed interpret-
ation of Coleopteran assemblages, Iiving and fossil,
remains the virtual lack of studies of Iiving assem-
blages (biocoenoses) and the fate of insect fragments
after death (taphonomy). Detailed examination of
insect biocoenoses were carried out by Lindroth
(1965) at Skaftafell and Dugmore (1981) has recently
provided quantitative data in synanthropic, hayfield
and bare ground situations by use of pitfall traps in
Eyjafjallasveit. There are similar limitations to inter-
pretation in detail elsewhere in Europe, particularly
in archaeological contexts (cf. Kenward, 1978). The
catchment of the Ketilsstadir bog and the representa-
tive nature of individual samples are difficult to
assess. Preservation favouring aquatic species in the
bog is perhaps evident in the BRl succession, where
the richer samples (table 2) are those containing water
beetles and fragments of their larvae; a vertical succes-
sion of alternating tussocks and pools through time
may be indicated by the fluctuating numbers. The
contrast between BRl/2 and KEl/5, samples which
were immediately adjacent and sealed by the —1357
tephra present a cautionary tale, which may be ex-
plained by the irregular nature of the bog surface,
although such is rarely evident in the disposition of
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