Full-text - Norsk entomologisk forening

Nocturnal moths 183
%60
50
40
30
20
10
April May June July Aug. Sept. Oct. Nov.
Fig. 5. Percentage of species of the population of
Noctuoidea likely to be trapped in IO-day periods
during the season.
activity covered the period from 22 June until
5 September. The result of his investigations,
also including material from Aall's collection,
was published (Schneider 1882). The publication
gives one of the most comprehensive
registers of lepidoptera from any part of
Norway in this century. The registration of
Schneider and Aall was mainly based on
catching with net and rearing larvae. Their
methods were hardly as effective for most
nocturnal species as the light-trap catches of
today. On the other hand, the diurnal species
and the nocturnal species which are not attracted
to light, are included in their material,
but not in light-trap catches. Schneider
(1882) gave no exact data for the abundance
of the species. He only mentioned if the species
were common or rare.
Therefore, a comparison of the fauna
based on different methods cannot be made
without many reservations. However, some
simple conclusions can be made. Schneider
(1882) mentions 28 species of Bombyces. Of
these, Aglia tau L. and Orgia antiqua L.
were not recorded in the light-trapped material
because they are diurnal species. Thyatria
batis L. was found in light-traps at
Bjelland, Tromey July 1968 and at Flageborg,
0yestad July 1969. This is less than
30 km from Grimstad as well as from Nes
Verk, where Schneider collected most of this
material. Eriogaster lanestris L. is the only
Bombyces species which has not been recorded
in the area in recent years. The lighttrap
catches gave 38 species, of which 14
were not mentioned by Schneider (1882). This
is a 50 % increase in number of species compared
to what he found.
Schneider (1882) mentioned 112 Noctuid
species, of which 12 were not caught in the
light-traps. Five of these are diurnal species.
They have all been recorded in the area in
recent years. Five were recorded by the author
in light-traps at other sites in the area. Only
one species, Catocola nupta L., has not been
seen in the area during the last 30 years. The
light-trap catches gave 12 Noctuid species,
of which 93 were not mentioned by Schneider.
This is a 91 % increase in the number
of species compared to Schneider's records.
Comparison between the two sites
Great similarities can be seen in the fauna
composition of the two sites. This was expected
because of the short distance (44 km)
between the sites. But some differences are
easy to find in the material. Some species are
more abundant at Grimstad, the southernmost
site, e.g. Agrotis segetum Schiff., Amathes
glareosa Esp., Axylia putris L., Luperina
testacea Schiff. and Orthosia cruda Schiff.
These are all species with southern distribution
in Fennoscandia (Nordstrem et al. 1969).
The higher number of species at Grimstad is
due to the influence of these southern species.
The first group of species more abundant
at A.mli, are Mamestra nana Hufn., Hadena
rivularis F., H. lepida Esp., and Polia hepatica
Cl., which are widely distributed in
Fennoscandia and Denmark (Nordstrem et al.
1969). Local variation must be the reason
why they are more common at A.mli than at
Grimstad, because both sites are within their
main range. The other groups are species like
Cersotis cuprea Schiff., Coenophila subrosea
Schiff, Brachionycha nubeculosa Esp. and
Lasionycta proxima Hb. which are northern
and high altitude species whose southern
limit is the coastal area of Southern Norway.
Changes in the population levels of
some species
The population level of some species changed
during the three-year period. Some species
declined. This is distinctly pronounced in
Agrotis exclamationis L., Heliophobus reticulata
Vill., Ochropleura plecta L. and Apatele
rumicis L. in both sites. Other species increased
in number, for instance Orthosia
CTuda Schiff. and Luperina testacea Schiff.