Stora Karlsö is a small island close to Gotland in the Baltic Sea of which the Hymenopteran

fauna has not been extensively studied before. In August 2014, a team of eight persons

carried out an inventory of Hymenoptera, mainly the parasitoid wasps and sawflies, on

the island. Sampling was done with Malaise traps for a period of 22 days, complemented

with vegetation sweeping, branch shaking and opportunistic handpicking during a five day

sojourn. As a result, about 200 species of parasitoid wasps and 14 sawflies are reported for

Stora Karlsö for the first time. Eleven species are reported as new to Sweden: The sawfly

Athalia cornubiae Benson, 1931, the gasteruptiid Gasteruption opacum (Tournier, 1877),

the diapriid Spilomicrus rufitarsis (Kieffer, 1911), the eulophid Entedonomphale bulgarica

Boyadzhiev & Triapitsyn, 2007, the braconids Bracon rozneri Papp, 1998 and Gnamptodon

decoris (Förster, 1862), and the ichneumonids Bathythrix maculata (Hellén, 1957),

Heterischnus filiformis (Gravenhorst, 1829), Lissonota picticoxis Schmiedeknecht, 1900,

Mesochorus tipularius Gravenhorst, 1829, Ophion brevicornis Morley, 1915, and Plectochorus

iwatensis (Uchida, 1928). Also the gasteruptiid Gasteruption opacum (Tournier,

1877) is reported new to Sweden based on a record from inventory by NJ in 2013. This

demonstrates how the knowledge of Swedish biodiversity can be substantially augmented

by a short and intensive collecting expedition. We strongly recommend that other places in

the country be subjected to similar efforts.