Characteristics of Leg Movements and Patterns of Coordination in Locusts Walking on Rough Terrain

A cinematographic analysis was made of locusts walking on a variety of terrains to determine the tactics used by single legs to find a site for support and the patterns of leg coordina tion when walking on rough terrain. Three tactics were used by individual legs for finding a support site: ( 1) rhythmic searching movements initiated when the leg failed to contact the substrate at the end of the swing phase, ( 2) a tactile reflex to lift the leg above an object contacted during swing phase, and ( 3) local searching movements once the leg had contacted a potential supporting surface. Animals did not adopt rigid gaits when walking on rough terrains. The wide range of stepping patterns was due mainly to variation in the timing of stepping in opposite legs of the same segment. However, there was a tendency for the stepping movements of opposite legs to be either 180° out of phase or exactly in phase. In- phase stepping of the middle legs was observed frequently when animals walked over a ditch or up onto an elevated ob ject. Once the forelegs had found support on either the far side of the ditch or on the elevated object, both middle legs stepped simultaneously and were then used together to move the animal over the ditch or up onto the object.