Norwegian Journal of Entomology - Norsk entomologisk forening

in the total material which includes a high
number of species from several families but with
rather few individuals of most species (Table 1).
Altogether 46 species were recorded, including
12 which were only identified to genus level.
Most species belonged to the family Linyphiidae.
Bolepthyphantes index from this family was the
most abundant species representing 38 % of the
total material. Nearly one quarter of the material
consisted of immature stages (mainly subadults)
of Pardosa sp. (Lycosidae) and Philodromus
sp. (Philodromidae). The next most common
species were three Linyphiids: Pityohyphantes
phrygianus (27 individuals), Helophora insignis
(20 individuals) and Tenuiphantes cristatus (12
individuals). One of the three Zornella cultrigera
individuals was taken in February far North in
Norway (Alta, Eibydalen with pine forest, about
100 m a.s.l.).
Phenology
As shown in Table 1, spiders were found on snow
during all winter months. In high altitude forests
patches of snow may remain even throughout
May and a male of B. index was sampled on
snow as late as 25 May at locality 4. Spiders may
occur on snow in mild weather during the whole
snow-covered period, but sampling was not given
priority when there were large patches of snowfree
ground, which is often the case during the
very early and very late winter phase. Two thirds
of the individuals were sampled towards the end of
the winter, in April. In this month air temperature
may reach 5-10 o C on sunny days and some snowfree
patches often exist where soil and vegetation
may reach even higher temperatures. Spiders
may easily colonise snow from these patches.
However, the month with the next highest catch
(64 individuals) was December. This was mainly
due to young stages of Pityohyphantes phrygianus
and adults of Helophora insignis.
The three most abundant species, B. index, Pardosa
sp. and Philodromus sp. were taken mainly in
April. For B. index, the activity maximum in April
was very clear, and was repeated several years and
in various localities.
Norw. J. Entomol. 53, 71-82, 22 May 2006
Activity on snow
Bolepthyphantes index is known to construct nets
over small cavities in the snow surface (Hågvar
1973). Such nets were observed regularly at
temperatures around or above 0 o C in March
and especially April during many years and in
several localities. An example was 3 April 2005
in locality 12, when 18 females and 3 males were
picked from about 20 nets. Most nets contained
only one female and were probably newly made,
constructed during a sunny day with 4-8 o C. The
distance between nets was about 5-10 m in this
occasion. On 17 April 2005 at locality 4, a net was
constructed across a ski track during less than an
hour, in sunny weather at about 8 o C. Usually, B.
index was sampled when walking on the snow.
Probably all the collected species are able to walk
on snow and a large part of the material consisted
of actively moving animals.
Except for B. index feeding on prey (mainly
Collembola) in their net, feeding by spiders on
the snow surface was only observed once. An
adult female of Helophora insignis was observed
feeding on a juvenile Anyphaena accentuata on
11 November 1971 at locality 2. It was calm and
overcast, and 2 o C.
In very warm and sunny weather in April,
subadults of Philodromus sp. are probably
starting “ballooning” from vegetation. On 18
April 2003 at locality 4, an individual was caught
when it was drifting slowly 20 cm above the ice
of a lake, hanging on its thread. It was sunny and
unusually warm (13-15 o C). The wind was very
faint, but this relatively large spider was easily
flying. Another individual was observed drifting
slowly about 2.5 m above the ice of another
lake, without loosing height. It was not caught,
but it was observed that the spider climbed its
thread during the flight. During the next two
days with similar weather conditions, a large
number of Philodromus subadults were observed
walking rather rapidly around on the snow and 21
individuals were sampled. Because many of these
were observed in the middle of lakes or large
bogs, with a long distance to snow-free spots and
penetrating vegetation, it is assumed that they had
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