Sunflowers are an increasingly important crop plant in the Czech Republic. The spider fauna of this crop has not been investigated yet. The aim of this study was to monitor the spider fauna of sunflowers and to study the seasonal change in the spatial and vertical distribution of this fauna. For this purpose a small experimental area was used where spiders on each single leave of 50 sunflower plants were visually checked at monthly intervals from spring until autumn. The density of spiders increased during the season reaching a maximum of seven spiders/plant in the autumn shortly before harvest. The spatial distribution changed accordingly, being random in spring and early summer and normal or aggregated toward late summer. Two spider species, Neottiura bimaculata and Theridion impressum (Theridiidae), dominated (96% of all individuals) throughout the season. These two species exhibited a different microhabitat preference: N. bimaculata individuals were found particularly on the lower sunflower leaves, T. impressum preferred higher leaves. The density of the spiders (per leaf) was independent of the density of two dominant pest species, aphids and leafhoppers.
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