Mechanisms of Wax Running

The complex of nine closely related Crematogaster (Decacrema) morphospecies represents an excellent model system to study the function of wax barriers and the biomechanics of wax running. Even though Crematogaster (Decacrema) ants are very similar in morphology [19,25], wax runners and non-wax runners differ strikingly in their running performance. Crematogaster (Decacrema) non-wax runners placed on vertical waxy Macaranga stems are at best capable of walking very slowly and often fall down [17]. Our initial study revealed a weak tendency for smaller ant species to be better wax runners, which may be explained by scaling laws (greater surface area to weight ratio in smaller ants). However, this effect was not significant, and many ant species even smaller than the specialized ant partners had problems climbing the waxy stems [17]. In a subsequent study [20], we disproved the hypothesis that wax running is simply based on larger adhesive pads relative to ant body size. Comparison of adhesive forces on a smooth Plexiglass substrate between wax runners and non-wax runners indicated even an inverse effect with wax runners clinging less well to the smooth substrate [20]. Wax running, however, is not necessarily a consequence of special adaptations of the tarsal adhesive system. The capacity to climb slippery stems could also involve behavioral and locomotory adaptations and other morphological traits. In the following section, we present a preliminary analysis of wax running in Crematogaster (Decacrema) ants by addressing three questions: (1) Is wax running capacity based on greater attachment or superior locomotion? (2) Are there any relevant morphological differences between Crematogaster (Decacrema) wax runners and non-wax runners? (3) How do the kinematics of climbing differ between wax runners and non-wax runners?

0 0

Post a comment