Fig. 2. `Tarsus catch' in aged animals. (A) Video image (from the side and below) of a 63-week-old adult with `tarsus catch'. Note that the right prothoracic tarsus catches on the tibia of the right mesothoracic leg. Inset: close-up of the tarsus catching on the mesothoracic leg. (B) `Tarsus catch' is not evident until 60 weeks post-adult molt, and the percentage of animals exhibiting this behavior increases up to 65 weeks. However, this percentage decreases in animals that live more than 65 weeks. (C) Gait pattern in an animal with `tarsus catch' in the right prothoracic leg. The swing phase is shown as filled boxes. Prior to `tarsus catch', this animal walks in an alternating tripod gait. The vertical line represents the time when the right prothoracic tarsus catches on the mesothoracic tibia. The ellipse illustrates the absence of swing in the left prothoracic and metathoracic leg due to `tarsus catch'. In addition, the length of the swing phase is reduced in the other legs to compensate for the absence of support by the left prothoracic leg. The animal recovers within one leg cycle.

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