Norwegian Journal of Entomology - Norsk entomologisk forening

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Hågvar & Aakra: Spiders active on snow in Southern Norway Table 1. continued 76 No. of Loc. no. Family and species Oct. Nov. Dec. Jan. Feb. Mar. Apr. winters (ind. sampled) Lycosidae Acantholycosa sp. 1 ms 1 6(1) Pardosa sp. 1ms 1ms, 2j 31ms, 7 1(7), 2(1), 4(41), 12j, 5fs 5(1), 6(1), 7(1) Xerolycosa sp. 1j 1j 2 6(1), 7(1) Philodromidae Philodromus sp. 1j 1j 1j 2j 32s, 13j 9 1(7), 2(3), 4(34), 7(3), 10(1), 12(2) Thanatus sp. 1ms 1 12(1) Tetragnathidae Pachygnatha degeeri Sundevall, 1830 1m 1 10(1) Pachygnatha listeri Sundevall, 1830 1m 1 3(1) Tetragnatha sp. 1j 1 4(1) Thomisidae Xysticus sp. 1ms 1 4(1) Zoridae Zora spinimana (Sundevall, 1833) 1m 1 4(1) Zora sp. 2ms 1 4(2)
landed after flying. The general snow depth was about 1 m. As seen from Table 1, Philodromus sp. has been collected on snow from several localities and years, and mainly in April. Weather conditions Weather data are not available from all samplings, but the temperature was usually noted. Figure 2 illustrates the climatic conditions during sampling, when weather data were recorded. If temperature varied during sampling, the mean temperature is given. Conditions when B. index was observed on snow are in black and show that this spider prefers temperatures above zero and calm, sunny weather. When the climatic data for all species are combined, the temperature range spans from –7 to 14 o C, with most observations around or above zero, often between 0 and 5 o C. However, several observations were also below zero. In most cases there was no wind, but the sky could be cloudy or clear. DISCUSSION Spiders on snow: An annual phenomenon with many species involved The present material from several localities and throughout several years shows that spider activity on snow is an annual, geographically general phenomenon. Spiders were found in all winter months. A large number of species participate in this activity, but most species are uncommon. Two studies from Northern Finland support this general picture. In a large material of more than two thousand spiders collected on snow, Huhta & Viramo (1979) documented activity throughout the winter except for the coldest period in February. As many as 102 species were recorded, most of them in relatively low numbers but with a few dominant species. A smaller collection by Koponen (1989) revealed fourteen species of which four were regarded as regularly active on snow. Huhta & Viramo (1979) suggested that almost any spider species present in the community Norw. J. Entomol. 53, 71-82, 22 May 2006 may be found on snow. Most of the species in the present material were also recorded by Huhta & Viramo (1979), except for the following six species represented by few specimens: Anyphaena accentuata, Diplocephalus latifrons, Mugiphantes suffusus, Obscuriphantes obscurus, Walckenaeria kochi, Pachygnatha degeeri, and the genera Acantholycosa, Araniella, Linyphia, Oedothorax, Thanatus, and Xerolycosa. A common feature of the present and the two Finnish studies was a strong dominance of Bolepthyphantes index on snow towards the end of the winter, in April. Although the snow spider fauna in Southern Norway and Northern Finland have many species in common, considerable differences exist Figure 2. Climatic conditions when spiders were sampled from the snow surface. One “observation” means that a species was present on one occasion at that condition, for instance temperature, but without indicating number of individuals. Data for the most abundant species, Bolepthyphantes index, are shown in black. Cloud conditions are indicated as clear sky, partly cloudy or completely cloudy (black). There was either no wind, a faint wind (+) or a strong wind (++). Finally, the number of observations are given for foggy weather or when it was snowing. 77
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N O R S K E N T O M O L O G I S K T
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Norw. J. Entomol. 53, 1-4, 22 May 2
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checked for this species, as T. pal
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Norw. J. Entomol. 53, 5-9, 22 May 2
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temperatures were more fluctuating,
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Hansen, V. 1927. Biller VII. Bladbi
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Solevåg: Coleoptera from Western N
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Clitellaria ephippium (Fabricius, 1
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INTRODUCTION The Norwegian myriapod
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Page 33 and 34: May 2005 3 ♀♀ leg. Spildra scho
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Norwegian Journal of Entomology - Norsk entomologisk forening

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