A major area of robot research and development comes under the category of biomimetics, or biomimicry, which looks to nature for inspiration. Some robots resemble different kinds of animals. For example, Boston Dynamics' Cheetah has broken legged-robot speed records at 18mph. (It can't match a real cheetah's 70mph.) The company is well known for its pioneering development of robots that use motions based on animals to run and maneuver, such as the BigDog.
Many robots modeled after animals are developed for military and first-responder applications. They can be based on insects, like the University of California, Berkeley's OctoROACH; worms, like MIT's Inchworm; and even jellyfish, like Virginia Tech's Robojelly. Many have similar applications, and some have similar funding sources. They are designed for reconnaissance, surveillance, and the ability to go where humans can't -- sometimes in tiny spaces, sometimes in dangerous territory, and sometimes in rugged or unusual terrain.
Click on the photo below to see a slideshow of 10 of these creepy-crawly robots.
The Multi-Appendage Robotic System (MARS) from Virginia Tech's Robotics & Mechanisms Laboratory looks like a giant spider with six legs instead of eight. Fabricated out of carbon fiber and aluminum, the robot's legs are spaced axi-symmetrically around its body, which lets it walk omni-directionally. Each leg uses a proximal joint with two degrees of freedom and a distal joint with one degree of freedom for added strength and rigidity. The goal is to develop a walking gait system for negotiating terrain with variations in height. The system is based on simplified biological neuron networks, arranged in subnetworks and subsystems to support the operation of another neural network: a central pattern generator (CPG)
that generates gait patterns based on feedback from all supporting systems.
(Source: Virginia Polytechnic and State University)