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

Table 4. The 10 most numerous staphylinid species in each of the 3 localities.
Abundance
No. JEL0Y As SKI
I Amischa analis Aloconota gregaria Amischa analis
2 Aloconota gregaria Amischa analis Aloconota gregaria
3 Aleochara bipustulata Dinaraea angustula Anotylus rugosus
4 Atheta fungi Philonthus ochropus Atheta fungi
5 Tachyporus hypnorum Anotylus rugosus Tachyporus hypnorum
6 Anotylus rugosus Atheta fungi Tachyporus chrysomelinus
7 Tachinus corticinus Tachyporus hypnorum Aleochara bipustulata
8 Tachyporus chrysomelinus Aleochara bipustulata Tachyporus obtusus
9 Aleochara bilineata Tachyporus chrysomelinus Philonthus ochropus
10 Tachyporus obtusus Philonthus cognatus Arpedium quadrum
fact that clay soil has a higher beetle population
than sandy soil has been generally found in European
fields (Thiele 1977).
Ski had extraordinarily few beetles, the numbers
being 7-10 for carabids and 27-49 for
staphylinids. This was probably due to the
heavy use of insecticides for several years and
the fact that herbicides reduced the weed cover
to almost nil.
Total number of carabids species caught at Je­
10Y, As and Ski were 62, 43 and 43, respectively,
the same for staphylinids being 101, 91 and 63.
The 8 most numerous carabids and staphylinids
are in the following treated separately, and comments
are given to some of the other species.
Numbers given in brackets are the mean number
of specimens per 100 trap days per year (calculated
mean from the numbers in Tab. 1 and
2). Breeding periods and .habitat preferences for
carabids not specifically mentioned are taken
from Lindroth (1945).
Carabids
Bembidion lampros (Herbst) was the most numerous
carabid, making up 24.2 % of the material. The mean
per year was highest at Jel0Y (I 1.8) and As (I 1.3)
while the activity density at Ski was only about 10%
of this. Lindroth (1945) says it prefers open and
sunny areas, and it is frequently mentioned as dominating
in European fields (Thiele 1977). The maximum
activity density was found in May-June (Fig.
2), when it reproduces, and among the lower catch in
July-Sept. several callow specimens, belonging to
the next generation, appeared.
The second most numerous carabid was Calathus
melanocephalus, (L.) making up 20.6 % of the material.
Like the previous species the mean per year was
highest at Jel0Y (6.0) and As (7.0). The Ski catch was
only about 5 % of that at JeI0Y. This is probably due
mainly to the irrigation, as it is known to prefer very
dry areas. It is said to appear on all sorts of soils, and
is common in European fields (Thiele 1977). A possible
preferance for sandy soil could not be confirmed
in the present investigation. Maximum activity
density occurred during Aug. (Fig. 3), when it is
known to reproduce. A smaller and varying peak of
acitivty in June-July, seen most easily in Jel0Y
1976, probably represents specimens tha, have overwintered
as adults, as shown by van Dijk (1973).
Pterostichus melanarius (Iiliger), the third most
numerous species, made up 11.0 % of the material.
At As (12.1) and Ski (0.9) it was among the dominating
species, which confirms what is previously
known from other European fields. It is said to be
lacking on sand and this was verified by the fact that
is was rarely caught at Jel0Y (Tab. 0. Maximum activity
density appeared in July-Aug. (Fig. 4), when it
reproduces. The smaller peak in May-June, most
easily seen at As 1979, probably represents animals
30
20
., 10
..,··..
60
: 40 • -- ._-- 121
• ~ 1H
.. 10
.. 20 10
• 10 41
..
II
~
~ 50 .1911
E 40 • 30
::,:. r
80 y 10
:. ~~,. ~~: :
• 30 n 20
~ 20 rl
11 1.
:"OS=·'~1
Fig. 2. Activity density for Bembidion lampros in
each of the 12 fields.
55