Fig. 5. Tarsus morphology in young and aged animals. (A) The tarsal pads of a 1-week-old adult are white in color (arrow), and the joints between the tarsal segments are flexible (not shown). (B) By contrast, the tarsal pads of an animal with `tarsus catch' are brown in color (arrow) and the joints are often stiff. (C) A nylon filament, producing a force of 29 mN, readily deformed the tarsal pads in young animals. (D) Pads of old individuals were hardened and were not deformed by the nylon filament. (E) The cuticle of tibia was removed to examine the internal morphology of these leg segments. The trachea and tendon (arrow) in the tarsal segments were healthy and silver in color. (F) The trachea and tendon in the tarsus of aged cockroaches are discolored, hardened and degenerated.