Jesse Grossman, Stephanie Held, Helen Michael, Theodore Salk, and William Severud
Department of Biology, Carleton College, Northfield, MN, USA, 55057
Abstract. Mate guarding, a result of sexual selection, is a post-insemination association between males and females. The neotropical millipede Nyssodesmus python exhibits prolonged riding behavior thought to be a form of mate guarding. To evaluate this hypothesis, we observed the riding behavior of millipede pairs in laboratory enclosures containing an additional male or female millipede. Mate riding behavior lasted significantly longer when an additional male was added, than an addition female. Both treatments lasted significantly longer than replicates with no additional millipede. We also conducted a field survey of N. python by observing sex ratio, behavioral characteristics, and population density at regular intervals along established trails at La Selva Research Station in Puerto Viejo, Costa Rica. In addition to reaffirming the 1:1 sex ratio, we recorded behavioral characteristics heretofore unpublished, and found that population was significantly clumped with densities high enough to increase the benefit of mate guarding. These results suggest that the riding behavior is mate guarding. Furthermore, we feel that N. python would make a model organism for further studies of mate-guarding behavior and sexual selection.