A fossil bumblebee (Hymenoptera, Apidae, Bombini) from the Middle Pleistocene Shiobara Group in Nasushiobara, Tochigi, Japan

Fossils of bumblebees and their kin (Bombini) are extremely rare, with only 15 occurrences from the Upper Eocene to Upper Miocene representing 14 species reported to date, all of which are extinct. Here, we report a new bumblebee (Bombus) fossil, a queen bee from the Middle Pleistocene of the Shiobara Group in Nasushiobara, Tochigi, Japan. The fossil was identified as Bombus (Megabombus) cf. diversus Smith, 1869, a species distributed throughout Japan. The fossil is large, with an estimated total body length of 24 mm. The new specimen is the first bumblebee fossil from the Middle Pleistocene, the most geologically recent occurrence of a bumblebee fossil, and the first fossil of an extant bumblebee species. This discovery suggests that modern bumblebee species originated between the Pliocene and Middle Pleistocene. This new fossil is a valuable resource for studying bumblebee speciation.