A behavioural analysis of the temporal organisation of walking movements in the 1st instar and adult stick insect (Carausius morosus)

SummaryThe coordination of protraction leg movements in free walking first instar and adult stick insects has been examined by film and video-tape analysis. The first instar insect uses two alternative modes of walking which differ in the step frequency dependence of the time required to complete one metachronal cycle of protractions and the duration of the protraction cycle (Figs. 2, 4). The adult uses only one of these modes and its step patterns show a persistent right-left asymmetry in the timing of leg movements (Fig. 7). Two alternative methods of changing direction were found (Figs. 5, 9) and they appear to be related to the two modes of walking used by the animal. A model based on inhibitory interactions between oscillators representing leg activity has been constructed to explain the step pattern changes in both modes of walking and the temporal asymmetry of the adult pattern. This model appears to be applicable to the walking behaviour of other insects including the cockroach.