Webs, diet, and fecundity of Theridion impressum (Araneae: Theridiidae).

摘要

Data on the webs, prey spectrum, density and fecundity of Theridion impressum from three different habitats (fields of sunflower, fiddleneck (Phacelia), and apple trees) in the Czech Republic are presented and discussed. The volume of webs was foundto vary between 5 (the first free instar) to 117 cm3 (subadult and adult specimens). The mean density of adult spiders per plant was 0.7 (sunflower), 1.5 (fiddleneck) and 1.2 (per apple branch). Spiders preferred to build webs in the upper part of vegetation or at the extremities of tree branches. The prey spectrum was assessed by collecting webs and identifying their contents. Prey items were primarily aphids (73%), Diptera (7.5%), and Coleoptera and Hymenoptera (both 5.4%). Pests comprised 90% of theprey; the remaining 10% was accounted for by natural enemies, pollinators and other insects. The number of insects captured in webs differed among study habitats (sunflower > fiddleneck > apple tree), though this difference was not statistically significant. Due to greater numbers of aphids in webs on sunflower, the mean prey length was significantly smaller on sunflowers than in other plots. An index of fecundity was obtained by counting the number of eggs in egg sacs. This varied from 48 to 156 per egg sac and was not significantly different between study plots. The number of eggs was strongly correlated with numbers of prey captured per spider.