What is the tarantula's primary defensive action before resorting to biting when cornered?

Employing urticating hairs from its abdomen

Tarantulas, when threatened but not yet feeling mortally endangered, utilize a specialized, non-venomous defense mechanism before escalating to biting. This primary defense involves kicking off barbed hairs, known as urticating hairs, which are located on the spider's abdomen. These microscopic structures, when propelled toward a threat, cause significant mechanical irritation upon embedding in the skin, eyes, or respiratory tract. Biting is generally reserved for situations where this initial warning is ignored or the threat persists or traps the animal, making the hairs the first active line of defense against perceived danger.