The anatomy and histology of the adult Argas (Persicargas) arboreus central nervous system are described and compared with these properties in other ticks. The single, integrated, central nerve mass (CNM) is formed by a fused supra-esophageal part (protocerebrum, cheliceral ganglia, palpal ganglia, and stomodeal pons) and a subesophageal part (4 pairs of pedal ganglia and the complex opisthosomatic ganglion). Single peripheral nerves (pharyngeal and recurrent) and paired peripheral nerves (compound protocerebral, cheliceral, palpal, pedal and opisthosomatic) extend from the CNM to body organs and appendages. Optic nerves, described in other Argas species, are not found in A. (P.) arboreus. Histologically, the CNM is enclosed by a thin-walled periganglionic blood sinus and invested by a collagenous neural lamella followed by a perineurial layer composed of glial cells and containing fine reticular spaces, a cortical layer of association, motor and neurosecretory cell bodies and glial cells, and inner neuropile regions of fiber tracts forming 5 horizontal levels of connectives and commissures.