o .eg an Jo of En1tomol0lD' - Norsk entomologisk forening

een planted, mostly as single trees, but also as
forest·forming stands.
Several small lakes and ponds are situated in
the area, mainly oligotrophic with sparse vegetation,
but a few ponds have a richer vegetation
dominated by Phragmites communis. The sea
shores are mainly rocks covered with lichen vegetation,
but there are also a few coves with halophytes
such as Puccinellia, Triglochin and
Atriplex.
In 1978 two light traps were operated in a rather
extensive heathland in Austre Loftmyra
(Fig. I). At the trapping site dry heath, dominated
by Calluna, Erica cinerea and Juniperus, al·
ternate with wet heath and ombrotrophic mire,
dominated by sedges and grasses, mainly Scirpus
caespitosus, Eriophorum vaginatum and
Molinia coerulea, but also with Calluna, Empetrum
nigrum and Erica tetralix. The vegetation
in the wettest parts were dominated by Eriophorum
angustifolium. The same year two light
traps were situated at Austervagen (Fig. I), in an
area with grassland and cultivated meadows, intensively
used as grazing land for sheep. The vegetation
at the trapping site was dominated by
sedges, mainly Carex spp. and Scirpus caespitosus,
and grasses like Sieglingia decumbens, Anthoxanthum
odoratum and Festuca vivipara. Juniperus,
Vaccinium uliginosum and Salix repens
were common, and on swampy' ground also
Myrica gale. A few trees and shrubs, mainly Be­
• tula pubescens, Sorbus aucuparia and Salix aurita,
were growing nearby.
MATERIAL AND METHODS
•
Sampling
,
The study was carried out between 1975 and
• 1980. The main sampling period was in 1978.
Day-active species were collected mainly in the
Vindenes area. Heathlands were particularly
thoroughly searched, but specimens were also
hunted in other types of habitats such as gardens
and cultivated fields. The rainy climate in northern
Sotra prevented regular sampling of dayactive
species, and the records of butterflies and
other day-active species are therefore based on
the collections made during the relatively few
days of fine weather. A few species were also taken
exclusively as larvae.
Most of the material was collected in light
traps. The light traps used were of a modified
Robinson type, fitted with mercury vapour
bulbs (Philips HPL-N 125 W). The trapping
periods were 3- 5 days.
The trapping at Austre Loftmyra and at Austervagenin
1978 were started on March 31. At
Austervagen the traps were operated without
major accidents until November 5, when a
period of cold weather set in. The traps at Austre
Loftmyra were situated at a rather wind-exposed
site, and the trapping had to be terminated
in September, when the traps were destroyed by
storm.
A total of 8636 and 7436 specimens of «Macrolepidoptera»
were taken in the traps at Austre
Loftmyra and at Austervagen, respectively.
The sections on species diversity, similarity, the
dominant species and flight periods are based on
these two sets of material. The localities will be
referred to as the «heath» and the «grassland».
In addition light traps were operated for shorter
or longer periods in several other localities,
Tab, I, Fig. I. These localities were chosen to
cover the main vegetation types in the area. However,
only records of species not taken at Austre
Loftmyra or at Austervagen in 1978 are included
in this paper.
Calculations
Based on the light trap catches from Austre Loftmyra
and Austervagen in 1978 the species richness
and equitability in the apportionment ofthe
specimens among the species in the two main
habitats have been studied. The species richness
is expressed using Menhinick (I964) index
d == Si VN, where S is the number of species and
N the number of specimens. The index has pro-
Table 1. Localities on northern Sotra sampled with light traps between 1975 and 1978.
'.. No. Locality UTM-reference Year Habitat type
1 Austervagen 32VKN803064 1977 -79 Grassland
2 Austre Loftmyra KN787062 1978 Cal/una heath
3 Av1aup KN779062 1978 Shore with saline vegetation
4 Eidesvag KM792999 1975-76 Cal/una heath
5 Geitneset KN805057 1978 Hardwood thicket with Quercus and Corylus
6 Landro skole KN782051 1978 Pond with Phragmites. and cultivated fields
7 Ongeltveit KN793044 1976 Hardwood thicket with Populus near smalllake
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