Magic Bees (previously Thaumic Bees) is a crossover mod between Forestry, Ars Magica, Equivalent Exchange 3 and Thaumcraft. It adds bees that do many things depending on which mods are installed alongside it.
When installed with Forestry it adds bees that create wither skull fragments, dragon egg fragments, and parts for magic frames that can change how bees work and live.
When Thaumcraft is installed it adds Thaumcraft essence to many Forestry items. In addition it adds bees that produce shards, move nodes, purify flux and regenerate nodes.
When Equivalent Exchange is installed it adds a bee that creates minium shards.
Finally, when Ars Magica is installed it adds bees that create items and essences from Ars Magica.
As of version 2.0.0 Thaumic Bees was renamed to Magic Bees and no longer requires Thaumcraft to be installed by default.