The abundance of large orb web spiders in the Swiss midland has declined drastically over the last 40 years.
The abundance of large orb web spiders in the Swiss midland has declined drastically over the last 40 years. The main reason for this is the shrinking food supply available to these insectivorous animals. This is demonstrated in a study conducted by researchers from the University of Basel and Ghent University (Belgium), as reported in the scientific journal Insects.
The approximately 48,400 known spider species around the world are among the most important insectivorous animals on earth. One group of these, the orb web spiders, spin conspicuous wheel-shaped webs. The perhaps best known and so far very common orb web spider species in Europe is the European garden spider Araneus diadematus. Apart from house gardens, their preferred habitats include parks, graveyards, hedgerows, forest edges and clearings.
Average population density of the spider about 140 times lower
The European garden spider is easily recognizable by the bright, cross-shaped mark on the upper side of its abdomen. The females of this spider species which measures 10 to 18 mm as adults, legs not included, spins webs with a diameter of about 30 cm. In late summer 2019, the entomologists determined the population density of the European garden spider in the Swiss midland in 20 representative habitats: they counted the spider webs in test plots ranging from 200 to 1,000 square meters and converted these values to the number of webs per square meter.
Read more at University Of Basel
Photo: European garden spider Araneus diadematus – adult female. CREDIT: Rainer Altenkamp
