Uwagi w sprawie jesiennych wędrówek pająków

Kajak, Anna

doi:ISSN 0424-7205

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Tytuł: Uwagi w sprawie jesiennych wędrówek pająków

Abstrakt:

Observations on the autumnal dispersals of spiders were effected during two years researches carried on on the vast area of low peat-bogs situated in the basin of Biebrza river. Samples were performed by means of quantitative scoop and by time method. A single scoop sample consisted in 25 scoop strokes, one series comprising 8 of such samples. Observation by the time metbod consisted in noting number of spiders perceived within 40 minutes. Samples took place on five natural meadows and on two artificial ones. The artificial meadows when compared to natura! meadows were showing the deficiency of green turf. Mass dispersals of spiders were observed 8 times, namely of lawn spiders (Linyphiidae, Lycosidae, Tetragnathidae) on the upper parts of herbs. In scoop catches this phenomenon distinguished itself as rapid, several or severa1 scores times, increase of the migrating species. Such impetuous growth of numbers took place on artificial meadows only, but was not observed on natural meadows (tab. l) in spite of the fact that all migrating species were found at the same time on both types of grassland. From descriptions of spider migrations in the relevant literature itfollows that in most cases they were observed also on grounds of scarcely follows developed turf (pastures, fields, park lawns, railroad embankments etc.) Composition of migrating species is similar on two artificial meadows. In initial migrations most frequent are species Thomisidae and Lycosidae. Thereupon the most numerous is Pachygnatha genus, and in the months of October and November it is the Linyphiidae which prevails (tab. II, III, IV). In 1953 the dispersals were not so frequent, but simultaneously more species were participating therein than in the year 1954 when migrations were repeated oftener (tab. III, IV). The dispersals of spiders are not connected with some strictly definited stage of development. Individuals of different age of various species were migrating. From the Thomisidae and Lycosidae families were migrating young individuals, from Tetragnathidae and Linyphiidae both young as adult ones, the latters being in prevailing number. From data to be found in literature one can conlude that the forms remaining active during the winter participate in migrations. And so it is possible to presume that the dispersals prove to be a flight of winter-active forms from poor turf territories, unsuitable for active endurance of the period of colds. It is suggested overall, that in the environments with poor turfs the same species are showing migrating tendencies, but no similar phenomena are to be noted on rich turf grounds.

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