WEB PLACEMENT IN SYMPATRIC LINYPHIID SPIDERS (ARACHNIDA, ARANEAE) - INDIVIDUAL FORAGING DECISIONS REVEAL INTER-SPECIFIC COMPETITION

The distribution of two sympatric web spiders. Frontinellina frutetoru m (C. L. Koch) and Neriene radiata (Walckenaer) (Araneae: Linyphiidae) was studied on an area oi forest regrowth in eastern Austria. Both sp ecies utilised significantly different heights on young conifer trees to construct their webs. F. frutetorum selected higher vegetation laye rs, N. radiata constructed its webs closer to the ground. This distrib ution may either be evidence of competition for web space or it may re flect specific distribution patterns unrelated to spider density. An e xperiment showed that when spiders of either species were released ont o vacant trees they selected similar vegetation heights for web constr uction. On trees already occupied by a heterospecific individual howev er, F. frutetorum placed its webs significantly higher and N. radiata significantly lower compared to web placement on vacant trees suggesti ng that F. frutetorum and N. radiata compete for web space. (C) Elsevi er, Paris.