Full-text - Norsk entomologisk forening

Terrestrial arthrofiods from Finse 125
summer season. According to Tullgren et al.
(1911), it is possible that Z. exulans has a
two-year life cycle. This would imply one or
two hibernations for the larvae, perhaps
including an accumulation of fat before
winter.
It is reasonable that pupae should also
show a slight decrease in water percentage
with increasing dry weight, representing fully
developed larvae of different weights. However,
after hatching, the water percentage
becomes remarkably stable for different
weight groups. There is no clear difference
between the sexes - the males perhaps have
slightly lower values.
The oxygen consumption increases markedly
from 5' to 20°C, in most cases following
a slightly exponential trend. The variation
within each temperature may be considerable
for a given species. This is mainly probably
caused by differences in the physiological
state of animals. as onlv animals which are
motionless or show very little movement
during the experiment were used for calculations
of the mean values. The listing of
values for clearly active animals shows that
respiration may increase manyfold during
activity. In N. niualis, very active animals
at 5 ' ~ might have an oxyben consumption
almost five times higher than animals at rest.
This fact shows that when calculating the
oxygen consumption of an individual during
natural conditions, both temperature variations
in the habitat, the length of each developmental
stage, and the activity pattern
of the animal must be taken into consideration.
The mean values recorded for resting
animals at different temperatures correspond
mainly with earlier data from arctic arthropods
(e.g. Scholander et al. 1953).
In a study on the aerobic and anaerobic
metabolism of the carabid beetle Pelofihila
borealis Payk. at Finse, Conradi-Larsen &
Ssmme (1973) found a respiration rate in
summer that was similar to the values we
have recorded for A. alfina. In an earlier
work, 0stbye (1963) recorded twice as high
respiration rates for N. niualis as found in
this study. The rates for N. gyllenhali in his
study were similar to those recorded here,
except for those at a temperature of 10°C,
where he found the values doubled.
Both beetles in his study showed the same
pattern of oxygen uptake with little or no
increase in consumption rate in the temperature
range between 10' and 20°C. Their
optima of temperature preference were found
to be within the same temperature range,
thus indicating a stabilizing mechanism for
metabolism in this range. Schmidt (1956)
observed corresponding regulation levels in
oxygen uptake in experiments on transpiration,
oxygen consumption, and prefetred
temperatures in some Carabus species. These
regulation levels, however, were relatively
small. In the present study, such regulation
levels may have been overlooked, because of
too large intervals between the temperatures
at which the respiration rates were measured.
Respiration data from eggs, pupae, larvae
and imagines in M. collaris and Z. exulans
show that the oxygen consumption per gram
and hour may vary markedly during development.
In both species eggs have the lowest respiration
rate at al1 temperatures. The two species
differ much concerning the oxygen consumption
of larvae. The mean value for M.
collaris larvae at 5OC is higher than the mean
value of Z. exulans larvae at 15OC. At al1
temperatures, larvae of the former species
have a respiration about four times higher
than the latter. This difference can be explained
by the difference in life cycle. The
larvae of M. collaris grow very fast and have
a larva1 period of about 12 days at 20' C.
Larvae of 2. exulans kept in culture at the
same temperature changed their weight very
little during 10 days. The loss of weight
during ecdysis seemed to be considerable, and
observations indicate that the larvae do not eat
for severa1 days during ecdysis, contrary to
larvae of M. collaris. In Z. exulans the larva1
period makes up the greatest part of the life
cycle, which, as mentioned earlier, perhaps
lasts for two years. In M. collaris the imagina1
stage covers the main period of the life cycle,
there is a new generation every year, and the
larva1 period lasts only a few weeks.
The respiration of pupae is clearly lower
than for imagines of M. collaris. In Z. exulans
the pupal respiration is similar to that
of larvae and females. Males have a somewhat
higher respiration, probably making
them better suited for swarming activity. The
values are similar to those of adult M. collaris.
In this species no distinction was made