NORSK ENTOMOLOGISK TIDSSKRIFT - Norsk entomologisk forening

102 Albert Lillehammer
to find any list for the inner areas. This article is based upon
investigations carried out in Suldalsl%gen, Storelva and Fl0gstadbekken
(a stream), the first-mentioned in the Districts of Suldal
and Sand (fig. I), the two latter in the District of Sauda. The
investigations were carried out during the years 1960-65. The
material consists of some 3600 nymphs, besides 62 imagines. The
method used for gathering was the board and frame method
described by Lillehammer (1964); in addition, a collector-net
known as a "Surber sampler" was used. Parts of the material
have been treated earlier (Lillehammer 1965).
Natural Conditions in Rogaland
Rogaland county divides quite naturally into the inner area,
Ryfylke, and the outer area, Haugesundshalv0ya (Haugesund
peninsula), Jaeren and Dalane farthest south, The natural conditions
differ considerably. In the eastern part of the county,
bed-rock predominates. In the west, it is over-layered by phyllites
upon which, again, there is a layer of deep-rock species.
The phyllites occur in the valleys and depressions, particularly
so, farthest west. In the inner area, the lowland frequently consists
of patches of sand deposited by rivers from the mountain
plateau which in the north-east rise to more than 1600 m. At
some places deposits of loam were found which originate from the
time the area was under water. On Jaeren, there are large moraine
deposits. The coastal climate is noticeable over large parts of
Rogaland. The mean summer temperature varies between 13"
and 15°C. The average for the yearlies on the whole somewhat higher
in Rogaland than elsewhere in the country. It is only in the innermost
fjord and valleys that the winter temperature falls below
minus 1°C. Thus there are more pronounced differences in summer
and winter temperature than at the coastal areas. In Rogaland
there is also a considerable difference in the rainfall; The
coastal areas have 1000 mm precipitation per annum, whereas in
the inner areas it is 2000 mm. These large climatic and geological
variations are found within a comparatively small area.
Four areas, differing markedly in natural conditions, were
selected for investigation :
I. Inner area, lowland, districts of Sand, Sauda and Suldal.
11. Inner area, mountain plateaux, districts Sauda and Suldal.
These three districts, together, cover a good 1900 km2,
that is, about 115 of the area of the county.
111. Lowland on Jaeren, very well cultivated areas.
IV. Haugesundshalv0ya, boggy land and heather heaths with
low mountains, to some extent, cultivated.