Model for how microtubule bundles regulate both polarized migration and contact repulsion in hemocytes. (a) Stabilized, Orbit-bound microtubules surround the cell cortex, whereas dynamic microtubules with Orbit-decorated plus ends probe the lamella by extending along actin filaments. (b) Dynamic microtubules coalesce during directed migration to form the bundled microtubule arm that becomes Orbit bound over the entire filament length. (c and d) Upon collision with another cell, there is initial alignment of the actin cytoskeletons (c), followed by microtubule arms colliding at the site of cell–cell contact (d). (e and f) Subsequently, microtubules are depolymerized in the vicinity of the cell–cell contact site (e), leading to cellular repolarization and contact repulsion (f).