Notes about spontaneous nesting of bumblebees’ queens in Belgium (Hymenoptera: Apidae). - To develop a rearing system for different wild bumblebee species, we experimented techniques for spontaneous nesting of wild queens. Our nest devices, which contain mouse litter as substrate, are used to attract wild bumblebee queens in search of a nest and to initiate brood construction. Over a total of four years of observation, we have installed 57 call nests with a 44 % success rate of nest initiation. However, this method has some limitations and does not show satisfactory results for ground-nesting bumblebee species.