Total numbers of bumblebees observed in the red clover fields in the past and present.

Bumblebee species were classified as long-tongued or short-tongued on the basis of tongue lengths measured in [24]. In both past and present studies, individuals belonging to B. terrestris (L.) and the B. lucorum complex (B. lucorum L., B. magnus Vogt. and B. cryptarum (F.)) were recorded as one species (hereafter B. terrestris). These species are difficult to distinguish in the field, but functionally similar [53], [54]. Notice that the sampling intensity differed between past and present studies, and the observed numbers of bees are, hence, not directly comparable.