Tama-kugel: Hardware and software for measuring direction, distance, and velocity of locomotion by insects

We have developed an accurate and inexpensive system for recording the path taken by a moving insect. The system consists of a low-mass ball on which the loosely tethered insect runs, an optical sensor to detect rotation of the ball, and software written in Visual Basic 6.0 that interprets and records the hardware's output. The ball floats on a cushion of air. The optical sensor's output is encoded as changes in x, y coordinates. The software monitors this output continually, and records each new x, y pair and the time at which it occurred. Since the system records only those data that have changed, the output files are compact. In its present form, the system is calibrated to detect changes in the animal's position roughly equivalent to one body length. It can accurately record the details of paths hundreds of meters long. We have applied the system to measure the paths taken by female crickets in response to male calls that differ in their temporal structure.