Orientation by Touch

Like many animals active in low-light conditions, cockroaches often use tactile cues to avoid obstacles and guide their locomotion. The long filiform antennae are posi tioned at an angle of approximately 30 degrees to the body's midline when the insect is walking or running in open spaces (P. americana). These serve as elongate probes that "cut a sensory swath" approximately 5.5 cm wide (Camhi and Johnson, 1999). The antennae are also used to maintain position relative to walls and other vertical surfaces. One antenna is dragged along the wall, and when it loses touch the cockroach veers in the direction of last contact. The faster they run the closer their position to the wall. Experimentally trimming the antennae also results in a path closer to the wall. The insects quickly compensate for projections or changes in wall direction, but depart from convex walls with diameters of less than 1 m (Creed and Miller, 1990; Camhi and Johnson, 1999). German cockroaches placed in a new environment tend to follow edges, but wander more freely in a familiar environment (Durier and Rivault, 2003).

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