Excavator: Stems. Nests of the nominate subspecies have been found in stems of large diameter of the following plant species: Foeniculum vulgare (Apiaceae); Crambe koktebelica (Brassicaceae); Sambucus nigra (Caprifoliaceae); Asphodelus sp.(Liliaceae); Rubus sp. (Rosaceae)
For subspecies assoroensis, nesting has been observed in stems of Rubus sp.(Rosaceae) (S.P.M. Roberts pers. obs)
Also, Grandi (1957) noted nesting of this species (probably ssp. assoroensis) in the stems of Conium maculatum (Apiaceae), and Sambucus ebulus (Caprifoliaceae).