Data from: Propulsion in hexapod locomotion: how do desert ants traverse slopes?

The employment of an alternating tripod gait to traverse uneven terrains is a common characteristic shared among many Hexapoda. Because this could be one specific cause for their ecological success, we examined the alternating tripod gait of the desert ant Cataglyphis fortis together with their ground reaction forces and weight-specific leg impulses for level locomotion and on moderate (±30 deg) and steep (±60 deg) slopes in order to understand mechanical functions of individual legs during inclined locomotion. There were three main findings from the experimental data. (1) The hind legs acted as the main brake (negative weight-specific impulse in the direction of progression) on both the moderate and steep downslopes while the front legs became the main motor (positive weight-specific impulse in the direction of progression) on the steep upslope. In both cases, the primary motor or brake was found to be above the centre of mass. (2) Normalised double support durations were prolonged on steep slopes, which could enhance the effect of lateral shear loading between left and right legs with the presence of direction-dependent attachment structures. (3) The notable directional change in the lateral ground reaction forces between the moderate and steep slopes implied the utilisation of different coordination programs in the extensor–flexor system.

采用交替三脚架步态（alternating tripod gait）通过崎岖地形，是多数六足总纲（Hexapoda）生物共有的典型特征。鉴于该步态或许是其生态成功的特定成因之一，本研究针对沙漠箭蚁（Cataglyphis fortis）的交替三脚架步态展开了分析，同时测定了其在平地运动、中等坡度（±30度）及陡坡（±60度）地形下的地面反作用力（ground reaction forces）与单位体重腿部冲量（weight-specific leg impulses），以期阐明倾斜运动时单条腿部的力学功能。实验数据共得到三项核心结论：（1）在中等坡度与陡坡下坡场景中，后肢均承担主要制动功能（运动方向上表现为负向单位体重冲量）；而在陡坡上坡场景中，前肢则成为主要动力来源（运动方向上表现为正向单位体重冲量）。上述两类场景中，主要制动或动力装置均位于质心（centre of mass）上方。（2）陡坡地形下归一化双支撑时长（normalised double support durations）有所延长，结合存在方向依赖性附着结构（direction-dependent attachment structures）的条件，该现象可增强左右腿部间的侧向剪切载荷（lateral shear loading）效应。（3）中等坡度与陡坡地形间侧向地面反作用力出现显著的方向变化，这表明伸肌-屈肌系统（extensor–flexor system）调用了不同的协调程序（coordination programs）。