Full-text - Norsk entomologisk forening

Norwegian stoneflies II 231
species also seem to differ in habitat preference
from area to area in Norway and
from that indicated by Brinck and Ulfstrand.
Brinck (149) mentioned Leuctra hippopus,
Leuctra nigra, Capnia bifrons and N emoura
flexuosa as eucoenic in small streams. Ulfstrand
(1968) found that Amphinemura sulcicollis,
Leuctra hippopus, Leuctra digitata and
Dinocras cephalotes were more abundant in
or even restricted to smaller watercourses,
while Amphinemura borealis, Leuctra fusca
and Isoperla obscura tended to avoid or be
sparse in small streams. However, Isoperla
obscura has also been reported from large
rivers in the Netherlands, Switzerland and
in the Tyrol (Brinck 1949).
In the following the distribution and observed
habitat preference of the various species
will be presented.
Fam. Perlodidae
Arcynopteryx compacta occurs in all parts of
the country (Fig. 25). The species was mainly
taken in Alpine areas. In southern Norway
the lowest locality was 700 m a.s.l. at Haldagsenoyri,
Atna. In the north Arcynopteryx
compacta occurs at all altitudes and in lakes,
outlets and in streams of different sizes. The
species occurs in the same types of habitats as
the Diura species. In the south it has only
been taken in running waters at higher altitudes
where it is the most common carnivorous
species. Localities in which it has been
taken range from about 700 to 1465 m a.s.!.
In Fig. 33 localities are plotted which indicate
the distribution trend in Fennoscandia.
Diura bicaudata occurs all over the country
(Fig 26), in the north in small and large
streams, lakes and lake outlets. The species is
most numerous and is the dominant carnivore
in all the investigated biotopes in the Pasvik
area which lie within the Sub-Arctic and
Boreo-montane sub-zones. This area seems
to contain the environmental factors nearest
to the optimum for this species. In southern
Norway it only occurs in lakes, mostly in
high altitude lakes in the Sub-Alpine and
Low-Alpine belts, but it may also be numerous
in large lowland lakes such as Mjosa and
Sperillen. The highest locality was about
1500 m a.s.l. Finnmark seems to be the central
area for this species. In Sweden the species is
a relict in some southern lakes (Brinck 1949).
Diura nanseni (Fig. 27) is the most widespread
carnivorous species in Norway. The
species has been taken in the same habitats
as Diura bicaudata in the north, but it is not
as common as Diura bicaudata in Pasvik and
Kautokeino. In the south Diura nansell,i is
the dominant carnivorous stonefly of all types
of running water below the Low-Alpine
vegetation belt. The species is absent from
the low coastal areas of south-western Norway,
although in the inner fjords it has been
taken from sea level to 900 m a.s.l. in the
Low-Alpine vegetation belt. The highest
record is 1300 m a.s.!. at 0vre Heimdal. Generally
Diura nanseni is most common within
the coniferous forest areas and in the Sub­
Alpine belt. According to Brinck (1949) this
species has not been taken south of lake
Viittern in Sweden.
Perlodes dispar (Fig. 28) has only been
found in three localities, all in the southeastern
part of Norway. The northernmost
find is from Sorkedalselven, Oslo, where the
nymphs were taken from unstable substratum.
In Sweden the species is mainly distributed
in the southern parts (Brinck 1949).
Isogenus nubecula (Fig. 29) has a wider
distribution and has been taken as far north
as in Tufsinga (700 m a.s.l.), North Hedmark.
The only locality where the species is numerous
is on stony substratum in the river
Glama south of Kongsvinger. In Fennoscandia
this species seems to have an eastern
distribution and has been taken in northern
Finland (Meinander 1965). The species is
absent in the southern parts of Sweden
(Brinck 1949).
Isoperla difformis (Fig. 30) occurs sporadically
in both northern and southern Norway.
It is only in the inner fjord area of the Oslofjord
that the species seems to be common,
and it seems to prefer places where there is
some silting or fine substrata beneath the
stones. It has only once been taken in western
Norway. The highest situated stream where
the species was taken was at about 700 m
a.s.l. In southern Norway it was taken only
in running water within the Boreal pine