Bee, the fourth abacus skill, builds on both the Ladybug and Spider levels but adds another complement concept, the 5 pair. The previous two levels taught complements involving two consecutive digits of a number. Bee now looks at two complement pairs involving only one digit of a number. For speed and efficiency the abacus created a top bead with a value of 5. This design introduced the need for two 5 pair complements, 4-1 and 3-2. Students learn to both add and subtract with 5 pair complements.