A COMPARISON OF SPONTANEOUS AND WIND-EVOKED RUNNING MODES IN CRICKETSAND COCKROACHES

We studied the effects of repetitive wind pulses on the escape behavio ur of tethered male cockroaches and crickets walking on a styrofoam ba ll (open-loop stimulation). The movements of this sphere were recorded to measure duration, forward and turning speed of walking and standin g phases during the insect's intended locomotion. All tested parameter s were quantitatively similar for spontaneous walking in both species. During stimulation crickets generated a sequence of running bouts ver y regular both in duration and forward speed. Interposed were standing phases the mean duration of which was inversely correlated with the w ind puff frequency. The mean distance run per period varied only bwtwe en 100 and 150 mm for the tested frequencies. Cockroaches often showed continuous high speed running for seconds, variable in duration and f ollowed by variable standing phases. Both parameters together with the mean forward speed of walking phases depended on the stimulus frequen cy in a non-linear manner. Therefore, the longest distance per period was run during stimulation with medium frequencies. Crickets were much better than cockroaches in turning away from the wind source in the r ange of 5-10 Hz stimulation. In cockroaches, the escape reaction was p artly retained after cercus ablation, but ceased completely when the s tyli were also removed.