Abundance and dynamics of wolf spiders (Lycosidae) in different plant communities
Institute of Plant Protection, Estonian Agricultural University, Kreutzwaldi 64,
51014 Tartu, Estonia; e-mail: email@example.com
The aim of the present work was to investigate the abundance and seasonal dynamics of wolf spiders in different plant communities.
During the study, 529 individuals of wolf spiders were collected. A statistical analysis of the results indicated that, compared with clover, the number of wolf spiders was significantly lower on rape, wheat and fallow during the whole period of the experiment. It appeared that wolf spiders preferred habitats where plant cover was greater and older. In comparison with rape, the number of wolf spiders was significantly greater in the fallow variant. Both on rape and wheat the number of spiders was lower throughout the experiment, and a comparison of these variants showed no statistical significance. A comparison of wheat with fallow revealed no reliable differences in the number of spiders, although there existed a slight tendency in favour of fallow. On rape and wheat the number of spiders was lower during the whole experimental period, and a comparison of these variants with clover and fallow showed no statistical significance.
The seasonal occurrence of spiders in the rape and wheat variants was different in comparison with the clover and fallow plots. In spring the activity of wolf spiders was low in the rape and wheat variants. The activity of wolf spiders significantly depended on the pest spraying times in the experimental fields. After treatments with Fastac (in May and June) in the rape variant and with a herbicide (in June) in the wheat variant, the number of spiders started to increase, however, this was only a small population peak and decreased very quickly. In the rape and wheat variants, the seasonal dynamics of the spiders showed one population peak in July, regardless of the treatments applied in May and June. A large number of juveniles was caught in pitfall traps of all test variants during the midsummer time. In May the number of spiders was low in the clover and fallow variants but started to increase quickly at the beginning of June. The seasonal occurrence of spiders shows a smaller population peak in June (on clover and fallow) and a large peak in July (only on clover). The peak was lower but broader in the clover variant. After the population peak, the number of spiders decreased again, because hay was made in the clover and fallow variants at the beginning of July. Spiders left those variants in one week (clover variant), or by the end of the vegetation period (fallow variant).