  A new class of traversable wormholes was recently constructed which relies
only on local bulk dynamics rather than an explicit coupling between distinct
boundaries. Here we begin with a four-dimensional Weyl fermion field of any
mass $m$ propagating on a classical background defined by a ${\mathbb Z}_2$
quotient of (rotating) BTZ $\times \, S^1$. This setup allows one to compute
the fermion stress-energy tensor exactly. For appropriate boundary conditions
around a non-contractible curve, perturbative back-reaction at any $m$ renders
the associated wormhole traversable and suggests it can become eternally
traversable at the limit where the background becomes extremal. A key technical
step is the proper formulation of the method of images for fermions in curved
spacetime. We find the stress-energy of spinor fields to have important
kinematic differences from that of scalar fields, typically causing the sign of
the integrated null stress-energy (and thus in many cases the sign of the time
delay/advance) to vary around the throat of the wormhole. Similar effects may
arise for higher-spin fields.
