Mandibular strength of nine European Osmia species of the subgenus Melanosmia. For each species, the force of the right mandible of three females was averaged except for O. alticola, O. maritima and O. steinmanni, for which only one or two specimens were available. Orange = nesting in self-excavated burrows in wooden substrate, green = nesting in preexisting cavities, blue = nesting in loose soil or litter, grey = nesting unknown (after Müller 2019 and references therein).