Butterfly Energy are purple butterfly-shaped units of health that serve as the player's life bar. Each world plus the main hive has one making there 6 butterflies to find for a max total of 12. If any health is lost, it can be restored by Slurp Shotting butterflies. The maximum Butterfly Energy can be increased by collecting Butterfly Boosters which can be found in each world. The duo starts out with six units of Butterfly Energy.
The duo can also extend the life bar by using the Wellard tonic, or reduce it with the Butterthree tonic. You can additionally make eating a butterfly gain 2 hearts with the Bruiser tonic.