A dynamic model of thoracic differentiation for the control of turning in the stick insect

Abstract

Leg movements of stick insects (Carausius morosus) making turns towards visual targets are examined in detail, and a dynamic model of this behaviour is proposed. Initial results suggest that front legs shape most of the body trajectory, while the middle and hind legs just follow external forces (Rosano H, Webb B, in The control of turning in real and simulated stick insects, vol. 4095, pp 145-156, 2006). However, some limitations of this explanation and dissimilarities in the turning behaviour of the insect and the model were found. A second set of behavioural experiments was made by blocking front tarsi to further investigate the active role of the other legs for the control of turning. The results indicate that it is necessary to have different roles for each pair of legs to replicate insect behaviour. We demonstrate that the rear legs actively rotate the body while the middle legs move sideways tangentially to the hind inner leg. Furthermore, we show that on average the middle inner and hind outer leg contribute to turning while the middle outer leg and hind inner leg oppose body rotation. These behavioural results are incorporated into a 3D dynamic robot simulation. We show that the simulation can now replicate more precisely the turns made by the stick insect.

Straight walking and turning on a slippery surface

“…We have found that the stepping patterns of the intact straight walking stick insect on the slippery surface are qualitatively very similar to those observed for freely walking stick insects (Cruse, 1976;Rosano and Webb, 2007) or tethered stick insects walking on a sphere (Dürr, 2005;Dürr and Ebeling, 2005). Similar movement patterns have also been reported for stick insects walking on an oiled glass surface and on a mercury surface (Graham and Cruse, 1981;Cruse and Epstein, 1982;Epstein and Graham, 1983).…”

“…As of now, there are no electrophysiological results in the stick insect elucidating the mechanism underlying turning. However, behavioral analysis has suggested that the front legs take a leading role in the organized execution of turns (Dürr and Ebeling, 2005) and a body trajectory analysis by Rosano and Webb (Rosano and Webb, 2007) supports this finding but suggested the additional contribution to turning by the posterior legs.…”

“…Previous studies that have investigated turning in insects have mostly looked at body trajectories and stepping patterns, either in freely moving animals [bee (Zolotov et al, 1975); fruit fly (Strauss and Heisenberg, 1990); ants (Zollikofer, 1994a;Zollikofer, 1994b;Zollikofer, 1994c); cockroach (Franklin et al, 1981;Jindrich and Full, 1999); stick insect (Rosano and Webb, 2007)] or animals under tethered conditions [e.g. stick insect (Jander, 1982;Jander, 1985;Dürr, 2005;Dürr and Ebeling, 2005); cockroach (Camhi and Nolen, 1981;Mu and Ritzman, 2005)], and they have mostly focused on the behavior as a task for the whole motor system.…”

Kinematics of phonotactic steering in the walking cricketGryllus bimaculatus(de Geer)

“…The dominance of the front leg movements in generating directional changes and adjustments has been reported in stick insects turning in response to visual stimuli (Dürr and Ebeling, 2005;Rosano and Webb, 2007) with the role of the middle legs still discussed (Rosano and Webb, 2007). There is no evidence in this species for hind legs making an active contribution to steering.…”

“…Different forms of asymmetric walking have been observed: stick insects increase their stepping frequency or step length on one side of the thorax relative to the other (Graham, 1972). Video recordings of walking stick insects performing visually induced turning (Dürr and Ebeling, 2005;Rosano and Webb, 2007) and of cockroaches with tactile-induced turning (Mu and Ritzmann, 2005) have all demonstrated the dominant role of the front legs in shaping walking direction.…”