Contact kairomones are essential for host-acceptance behaviour by female parasitoids. In the solitary endoparasitoid wasp, Diadromus pulchellus, this behaviour depends mainly on compound(s) in the cocoon of their host, Acrolepiopsis assectella pupae. Extracts of empty cocoons and polypeptides extracted from cocoons were tested in acceptance behaviour assays using cotton fibre lures bearing extracts. Extractions with solvents of increasing polarity indicated that the active compounds were polar, while SDS-PAGE showed that four glycopolypeptides contained enough information to trigger host-acceptance behaviour in female wasps. This kairomonal activity was found to be due to the protein moieties, and was independent of any glycosylation. These four glycopolypeptides might be two variants of two soluble sericin-like polypeptides differing in their degree of glycosylation.