The escape behavior of the cockroach Periplaneta americana - I. Turning response to wind puffs

1. Cockroaches (Periplaneta americana) responded to controlled wind puffs with stereotyped turns away from the source of wind. This was followed by running in more varied directions (Fig 3, 5). 2. Control experiments indicate that the wind direction, and not other cues from the wind stimulator, provides the directional information for the turn (Fig. 7). 3. Cockroaches with the ventral surfaces of their cerci covered were unresponsive to controlled wind puffs. However, covering the dorsal surfaces left the responses essentially intact (Fig. 9). Covering the left cercus caused turns to be misoriented to the left (Fig. 11). Rotating both cerci toward the left led to a corresponding misorientation of the turn (Fig. 10). Thus the cockroaches appeared to employ only wind receptors on the ventral surfaces of the cerci (the location of the filiform hairs; Nicklaus, 1965) to detect all directions of wind puff and to evoke the turning behavior. 4. The initial movements of each metathoracic leg in response to wind stimuli depended upon wind angle (Fig. 12). These leg movements were consistent with earlier neurophysiological data on the motor outputs to the legs from giant interneurons which respond selectively to wind from different directions (Ritzmann and Camhi, 1978; Westin et al., 1977). 5. The turning response was properly oriented, and the leg movements properly directed, even when sampled during the first 0-16 ms of movement (Figs. 12, 13). This presumably was prior to the time when feedback from the animal's own turning movement would be available to influence the turn. Thus the turning behavior may be executed in an open loop manner. 6. These findings are discussed in relation to the role of identified giant interneurons in the oriented evasive behavior, and the possible role of this behavior in nature.