The term 'palpus' is a six-letter word which refers to a type of appendage found in some invertebrates, such as insects and crustaceans. It is also known as a FEELER, due to its sensory function. Palpus are thin, flexible structures that are used to detect changes in the environment, such as vibrations or air currents. They are typically located near the head of the organism and can be used to help the organism find food or avoid predators.