Meeting Abstract

93.2  Monday, Jan. 6 13:45  Insects traversing grass-like vertically compliant beams LI, C*; FULL, R.J.; Univ. of California, Berkeley; Univ. of California, Berkeley chen.li@berkeley.edu

Small running animals encounter more challenging terrains than larger ones. These terrains can be filled with three-dimensional, multi-component obstacles. Here, we study cockroaches (Blaberus discoidalis) moving through grass-like, vertically compliant beams during escape. We created an apparatus to systematically control and vary geometric parameters and mechanical properties of model grass that include their height, width, thickness, lateral spacing, fore-aft spacing, angle, number of layers, stiffness, and damping. We observed a suite of novel locomotor behaviors not previously described on simpler 2D ground. When model grass height was larger than 2 times the animal’s body length and the lateral spacing was smaller than 50% of the animal’s body width, the animal rolled its body onto its side to rapidly maneuver through the narrow gaps between the model grass. 50 percent of the time, animals (N = 6 animals, n = 361 trials) locomoted on their side through three layers of grass within 2.1 ± 1.3 seconds. We hypothesized that the animal’s slightly curved, oval body shape (resembling a slice of an ellipsoid) facilitated its traversal. To test our hypothesis, we modified the animal’s body shape by adding a rectangular plate onto its dorsal surface (N = 6 animals, n = 374 trials). The probability for traversal on its side through grass decreased to 5% and the travel time increased to 5.8 ± 3.2 s. Upon removal of the rectangular plate (N = 4 animals, n = 225 trials), the probability and time for traversal on its side through grass recovered to 47% and 2.7 ± 2.1 s, respectively. Locomotor geometry effectively coupled to terrain dynamics can enable negotiation of multi-component obstacles, and provide inspiration for small robots to navigate extended terrain with minimal sensing and control.