TRICHIOSOMA-NANAE SP-N, A MONOPHAG ON BETULA-NANA FROM FINLAND (HYMENOPTERA, CIMBICIDAE)

Trichiosoma nanae sp.n. is described from Finland. The species occurs in pine bogs, where the host plant of the larva, Betula nana Linnaeus grows. Records are given on its distribution in Finland. The thin cocoons, usually situated near the apex of twigs of the host plant, are frequently attacked by birds. Eight species of Ichneumonidae and one species of Torymidae (Hymenoptera) have been reared from cocoons, of which about 30 percent are parasitized. The three most common parasitoids are Agrothereutes mandator (Linnaeus), Rhorus mesoxanthus (Gravenhorst) and Protarchus testatorius (Thunberg).