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

Table 6. Sex ratio and median day of species taken in 100 specimens or more in the light traps in the Cal/una
heath at Austre Loftmyra and on the grassland at Austervagen in 1978. Median day have been calculated for
the females only in species were 25 or more females were caught. The median day given for Pachycnemia hippocastanaria
refer to the spring generation.
~
)
SPECIES n %9
cl
Median day
9
Geometridae
Entephria caesiata 185 10,3 15.7
Eulithis testata 379 4,0 18.8
E. populata
188 4,3 9.8
Thera cognata
2841 8,6 3.8 5.8
T. juniperata 171 1,2 13.10
Perizoma didymata
150 4,7 8.8
Eupithecia pusillata
291 22,7 16.8 17.8
Pachycnemia hippocastanaria 242 14,0 19.5 22.5
Alcis repandata 179 8,4 18.7
Gnophos obfuscata 188 8,5 26.7
Noctuidae
Euxoa obelisca 181 6,6 14.8
Rhyacia grisescens 128 14,1 9.8
Chersotis cuprea 159 22,0 13.8 15.8
Noctua pronuba 381 8,9 12.8 14.8
N. comes 194 12,4 12.8
Paradiarsi glareosa 171 22,8 3.9 6.9
Lycophotia porphyrea 2063 13,9 16.7 27.7
Diarsia mendica 400 14,6 17.7 29.7
Xestia castanea 183 11,5 17.8
X. xanthographa 169 10,1 17.8
Cerastis rubricosa 141 5,7 30.4
Ceramica pisi 107 3,7 5.6
Cerapteryx graminis 904 11,9 6.8 9.8
Orthosia gothica 546 9,7 1.5 6.5
Aporophyla nigra 595 23,7 5.9 6.9
Amphipyra tragopoginis 120 20,0 1.9
Apamea monoglypha 433 28,6 2.8 6.8
A. lateritia 329 14,9 2.8 3.8
Photedes minima 124 0,8 23.7
Amphipoea IUfens 762 8,7 22.8 19.8
A. crinane,lsis 594 7,7 14.8 19.8
Celaena haworthii 228 0,4 10.8
Stilbia anomala 235 3,0 8.8
were lower than on the neighbouring grassland.
This difference is undoubtedly rootet in the fact
that the grassland has a richer flora (0vstedal
1978), and more Macrolepidoptera can hence
find suitable foodplants in this habitat.
However, while the species richness among
Noctuidae in the heath was only slightly lower
than on the grassland, the difference between
the two habitats was more pronounced in Geometridae.
S0rensen's quotient of similarity also
shows that the Noctuidae faunas in the two habitats
are more similar than the Geometridae
faunas. This difference might be connected with
the windy climate. Based on light trap catches
Williams (1940) demonstrated a strong negative
correlation between wind velocity and the flight
activity of insects, and also that Noctuidae are
less affected by wind than the average other insects.
The generally more slender, broad-winged
Geometridae might therefore be more vulnerable
than the Noctuidae in the open wind exposed
heathlands on northern Sotra, and Geometridae
from neighbouring habitats might therefore
generally be more reluctant to fly across
heath terrain. The higher similarity between the
Noctuidae faunas in the heath and on the grassland,
as shown by S0rensen's quotient, might
accordingly be an expression of a higher dispersal
ability of Noctuidae in a windy climate. The
flight activity of the Geometridae inhabiting the
heaths seems, however, not to be seriously supressed
by wind, as the family constituted 40 %
101