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Norwegian stoneflies 11 245
compacta often dominate high-altitude
streams, sometimes together with Amphinemura
standfussi. In lakes Capnia atra and
Diura bicaudata usually dominate, although
sometimes with N emurella pieteti, N emoura
cinerea, or N emoura avicularis. In the southern
areas Capnia atra is absent and there
Diura bicaudata and N emurella picteti are
often most numerous. In northern Norway
Capnia atra and Diura bicaudata may dominate
the fauna of both lakes and streams.
According to Rauser (1971), the Taeniopteryx
nebulosa and lsoperla obscura are
characteristic for lentic currents of the
boreal zone. In the streams west of Oslo
which Rauser says belong to this type, I soperla
obscura has not been recorded at all.
If the species is present there, it is rare, and
not characteristic. Even T aeniopteryx nebulosa
is not characteristic for this stream type,
as the species is just as common in stony
streams with moss vegetation in the mountain
areas.
Finally Diura nanseni should be the characteristic
carnivore stonefly species of the
hilly-land and piedemont currents of the
boreal zone, and not the Dinocras cephalotes
mentioned by Rauser. Dinocras cephalotes is
only found in isolated localities. Thus the
above examples serve to show that Rauser's
(1971) system for the northern areas is invalid.
Attempts to use the systems presented by
Hynes (1941) and Brinck (1949) for the
Norwegian fauna have also had little success.
Brinck (1949) divided habitats into spring,
trickles, small eutrophic forest streams, southern
streams, northern streams, southern rivers,
northern rivers, jokks, ponds, southern lakes
and northern lakes. He also stated that the
classification based on different perceptible
environmental conditions only serves as long
as there is a true correlation between the
species and the habitats, i.e. a habitat which
does not correspond to a specific zoom has
no authorization in the classification. Most
of the Norwegian landscape is quite different
from the Swedish, and this certainly makes
the environmental factors act differently in
Norway and in Sweden by producing another
faunal association out of the total environmental
impact on each species. Not all the
habitats listed by Brinck (1949) fit well into
the Norwegian landscape. This is illustrated
by reference to western Norway, where high
mountains provide cold water from melting
snow for most of the summer. The water
flows down into the lowlands which have a
more or less atlantic climate. According to
Brinck's (1949) classification, most of the
larger streams have temperatures which fit
well into the jokk type. Along much of their
length they would also be of the jokk type
regarding substratum and stream velocity,
but between these parts there are still flowing
silting sections at all attitudes. Faunistically,
however, they do not belong to either the
jokks or the northern streams. Typical inhabitants
of the jokks, Capnia atra and Arcynopteryx
compacta, are absent in the southern
parts and the streams do not have the
same association of species which are typical
for the northern streams of Brinck (1949).
Variation along the length of a single
watercourse is most pronounced in western
Norway, but also occurs in most other areas
of the country. Therefore no attempt will
be made in this study to classify streams.
Ulfstrand (1968) discussed the classification
of lotic biotopes and their animal communities
and made the following classification:
1. The biotope classification, where he
concluded that a substratum classification
was the most suitable. 2. The community
classification. He mentioned the attempt made
by Berthelemy (1966) to adopt faunistic criteria
in his studies. These were largely unsuccessful
and he concludes 'Community classification,
based on characteristic species or
species constellations (f. Berg 1948) will generally
have only regional applicability'. In the
present work Lufstrand's (1968) conclusion is
reinforced by the faunistic differences observed
in the seven investigated areas of
Norway and the considerable differences in
the biotope preferences of the species in northern
and southern Norway indicate that generalizations
should be avoided where possible.
THE STONEFLY FAUNAS OF
DIFFERENT AREAS GROUPED
ZOOGEOGRAPHICALLY
The zoogeography of stoneflies has been discussed
by authors such as Brinck (1949),