The volumes of brains and major brain regions were compared between European (EHB) and African (AHB) honey bee workers. The brain volume was not significantly different between the two bee races. The overall composition of major brain regions appeared similar except for the lobes of the mushroom bodies, which were significantly larger in EHB. Discriminant analysis indicated that brains from EHB could be distinguished from those of AHB based on the volumes of the central body together with either the mushroom body lobe or the mushroom body calyx. Whether learning and memory capacities differ between AHB and EHB based on the size of mushroom body lobes and whether the differences are adaptive due to the environments where EHB and AHB originated are discussed.