Blåsvarta björkstekeln, Arge pullata (Hymenoptera: Argidae), i Sverige och första fyndet i landet av dess parasitoid Scolobates testaceus (Hymenoptera: Ichneumonidae)

Abstract

The European birch sawfly Arge pullata (Zaddach) was found for the first time in Sweden in the early 2000s. According to a report in the local newspaper it was present on the Falsterbo peninsula, Skåne province, from 2000 at the latest, and in the following years a number of records were reported from the same restricted area. Subsequently it has expanded its range in southern Sweden. It is unusual that a sawfly receives public attention, but in the case of this species its presence is of general interest because of the toxic properties of its larvae, which can be consumed by cattle and pets. Here we give a short description of the biology of the species, its spread in southern Sweden, and report the first record in Sweden of its parasitoid Scolobates testaceus Morley, which is also the first record of S. testaceus from A. pullata. We speculate that this and possibly other natural enemies have attenuated the spread and build-up of large populations, which were feared when the species was first detected in the country.