Insekter och spindlar i anlagda våtmarker: intressanta fynd från en systematisk undersökning i Uppland och södra Halland

Abstract

Wetland area has decreased dramatically compared with preindustrial times, and in many agricultural areas almost all wetlands have been drained to gain cropland. The trend has in recent years been reversed because society has realized the many benefits of wetland functions, such as for nutrient retention and flood control. In this study we inventoried 75 wetlands in Uppland and Halland for insects and spiders with Malaise traps, pitfall traps and suction sampling. Most included wetlands are constructed, because the main purpose was to examine if these wetlands also can be good for arthropod diversity, but we also included some more natural wetlands as comparison. In total, we identified more than 25,000 individuals of more than 900 species of Coleoptera, Araneae, Diptera and Heteroptera. We found one new species for Sweden, Hilara manicata Meigen 1822, and 37 new regional records. A large number of species found are considered threatened or else rare. Some wetlands close to Mälaren were particularly interesting, with three species (Hypsosinga heri (Hahn 1831), Rhaphium antennatum (Charlier 1835) and Bagous robustus Brisout de Barneville 1863) that have no records nearby during recent times. These and other species found in the study show that constructed wetlands can provide good habitats for arthropod biodiversity and rare species, particularly if wetland shores are grazed and trampled by cattle.