Two new Japanese halictine bees, Lasioglossum (Lasioglossum) esoense Hirashima et Sakagami sp. n. and L. (Evylaeus) ohei Hirashima et Sakagami sp. n. were described, together with some biological notes. In both species the brood cells are connected to the main nest burrow by means of short and narrow laterals. Both species have one generation and one brood per year. L. esoense is strictly solitary. In L. ohei, many nests contain more than one burrow. Each burrow is usually occupied by one female, which seem to work in her own burrow independently from other individuals. But the occasional deviation from such social pattern, the common use of the same burrow by more than one female is suggested in some instances. L. ohei is remarkable by the cephalic polymorphism in males. The small males have normal head, while the larger ones monstrously developed quadruple head with enormous mandibles and genal processes. These extremes are linked with the intermediate type, forming a continuous allometric series.