Descending control of body attitude in the cockroach Blaberus discoidalis and its role in incline climbing.

Unlike intact animals, cockroaches with bilateral circumoesophageal connective lesions have difficulty climbing up smooth inclines. Typically, they slipped badly or even fell over backward before traveling more than 1.5 body lengths up the incline. The major problem involves increased slippage of the front and sometimes middle legs. Periods of front leg slipping are correlated with excess body elevation that pushes the height of the head to 11 mm above the substrate. Intact animals control body attitude very well on the incline, only rarely rearing above 11 mm. Cockroaches with bilateral circumoesophageal connective lesions spend considerable time above this critical amplitude and slipping increases with amplitude above that value. We conclude that circumoesophageal lesion compromises the insect's ability to control body attitude on the incline and this deficit contributes to the inability of lesioned cockroaches to climb steep inclines. A separate body attitude deficit was noted on steps. Upon climbing to the top of a barrier, intact animals bend their body between the first and second thoracic segments. This action maintains good leg mechanics throughout the climb. Cockroaches with bilateral circumoesophageal connective lesions fail to perform this downward flexion. A beneficial role for similar body flexion in simple robots is described in the Discussion.