Full-text - Norsk entomologisk forening

Symphyla and Pauropoda 163
Table 111. Number of symphyls (S) and pauropods (p) recorded at the Sl~rstad locality. Number of
soil samples in brackets.
1972:
21 Sept.
25 Oct.
6 Dec.
Depth of samples in cm
0-3 3-6 6-9 9-12
1973:
9 Feb.
22 Mar.
10 May
17 June
4 Aug.
4 Sept.
Many pauropods but no symphyls were found
in soil samples from the uppermost 3 cm of
the humus. Pauropods were also extracted
from the moss layer. Al1 belonged to P. lanceolatus.
The results of Symphyla and Pauropoda
from the regular samples are seen in Table
111. The only species found were S. sz~bnuda
and P. lanceolatus. The fraction of soil cores
with pauropods from each sampling day
varied from O to 30 OJO, with a 17.2 OJO average
for the whole sampIing period. The highest
number of pauropods in one soil core was 30.
The proportions of adults and the different
instars of P. lanceolatus from each sampling
day are seen in Table IV. Third instar to
adult stages of symphyls were found throughout
the year in both areas.
DISCUSSION
Symphyla
According to Michelbacher (1949) the symphyls
are found in al1 soil types, but they
prefer soils with an open texture as they are
not capable of burrowing their own runways
in the soil.
In the present survey, the symphyls were
not found in the uppermost part of the soil
profile (Tables 1 and 111). In those instances
where they were found between 6 and 9 cm
depth at Slerstad, the raw humus layer was
not more than 6 cm thick. At Nordmoen the
humus horizon is much thinner, and here the
symphyls are often found between 3 and 6
cm depth. It appears therefore that the transition
between the mineral soil and the humus
is an upper border for the vertical migration
of the symphyls. The only possible exceptions
to this are the two symphyls found between
3 and 6 cm depth at Slerstad 17 June 1973.
However, it should be pointed out that the
mineral soil rose a few mm in this soil slice.
It is well known that symphyls are found
in the deeper soil (Salt et al. 1948, Michelbacher
1949, Edwards 1958). Nevertheless,
the conditions which these animals encounter
in the mineral soil are quite different from
soils which are sually considered to be
optimum for symphyls. Edwards (1958) found
that sand was the least favourable of symphyls.
From these observations one would
expect that the symphyls, like most of the