Division of labor and structural plasticity in an extrinsic serotonergic mushroom body neuron in the ant Pheidole dentata

► We examined a conserved serotonergic neuron in an ant brain. ► The neuron showed greater branching complexity in major workers than minors. ► Mature majors had more branching (absolute count) than newly eclosed majors. ► The neuron likely synapses onto neurons receiving olfactory input. ► The neuron may be associated with sensory mechanisms underlying division of labor.