Fróðskaparrit - 01.01.2008, Síða 178

176
DISTRIBUTION AND THE IMPACT OF OUTFIELD DRAINACE ON CARABIDS
(COLEOPTERA, CARABIDAE) IN NORTH WESTERN EYSTUROY, FAROE ISLANDS
only found one specimen, so it seems that
Bembidion bruxellense is quite rare in the
Faroe Islands.
The reason for us getting fewer species
than Bengtson (1981) is related to the fact
that our work does not cover as many habi-
tats as does the work by Bengtson (1981)
where places like infields and higher moun-
tains also were investigated. Bengtson (1981)
found many species in the infields which
were not covered in this project.
The difference in abundance shown by
some species between the early part of sea-
son and later part of season, and also re-
garding altitude, is likely related to repro-
ductive cycle and habitat preference. All
carabids have difference in abundance dur-
ing the year but our season-cover was not
long enough to see it all (Lindroth, 1985 and
1986). Patrobus septentrionis is a biennial
species, which overwinters as adult; the new
P. septentrionis emerge in mid summer (June
to August) and adults are usually collected
in June and July (Lindroth, 1985; Erikstad et
al„ 1989). Carabids that reproduce the year
after emergence often show little activity
after emergence, this is an adaption to pre-
serve the mandibles - used when eating -
for the breeding season the next year (But-
terfield, 1996). So the reason for the lesser
abundance of Patrobus septentrionis in the
later part of the season might be related to
low activety.
Calathus fuscipes imagines emerge in
early sommer, so the higher catch of this spe-
cies in the earlier part of the season, which is
mid-summer, might be related to its emer-
gence (Lindroth, 1986). Butterfield (1996)
finds that at 305 m and 430 m altitudes in
northern England new Calathus fuscipes
emerge in late July and they overwinter to
enter the breeding season the following
spring. It is very likely that Calathus fuscipes
also has a biennial reproductive circle in the
present areas, since there is a relation be-
tween northern climate and biennial repro-
ductive cycle (Lindroth, 1985; 1986: Butter-
field 1996). So the higher abundance of
Calatus fuscipes in the early part of the sea-
son might be related to the emergance of
new C.fuscipes in July.
Nebria salina emerges in the spring, and
after a while enters a state of dormancy dur-
ing mid-summer but starts activity again in
the late summer in combination with repro-
duction (Lindroth, 1985). Theactivityfound
by us in late summer by Nebria salina is likely
associated with reproduction and is an ex-
planation of the higher abundance of N.
salina in the late part of the season com-
pared to the early part. Notiophilus bigutta-
tus breeds in the spring and the new beetles
emerge in summer and autum (Lindroth,
1985); this is possibly the reason for us col-
lecting more N. biguttatus in the late part of
the season
Carabus problematicus has a biennial
cycle in northern climates with the adults
emerging in the late summer and breeding
in the autumn the year after (Lindroth,
1985), this explains the higher abundance of
Carabus problematicus in the later part of
the season.
The distribution shown by Calathus
fuscipes only being found on the southwest
facing slopes is likely related to them being
relatively warmloving and preferring rela-
tively dry habitats (Ashworth, 1973; Lin-
droth, 1986; Butterfield, 1996). Calathus
fuscipes had significantly higher abundance