Aggregative Spinnennetze - weitere Funde in Deutschland und mögliche Erklärungen

In contrast to social spider webs aggregative spider webs are defined as incidental and non-functional. Three new records of large (3-10 meter) aggregative spider webs in Germany are presented. In one case (cut fir tree) 11 spider species were recorded from the same web. Two main reasons for the occurence of large aggregative webs are hypothesized: 1. Optimal (weather) conditions for ballooning behaviour may cause a mass occurrence of spiders, which are able to cover vegetation structures with their draglines. 2. Disturbances in the spider habitat (e.g. cutting trees) may cause a movement of spiders to higher (then absent) strata, which may cover also vegetation with huge webs. In both cases spiders may aggregate on the surface of vegetation structures and webs are more dense at their higher points. A parasocial aggregation cannot be excluded, but according to the new observations this seems to be unlikely.