Path selection in cockroaches.

In gregarious insects, the exploration and the use of the home range can involve both individual navigational abilities and/or chemical trails. Trail formation can result from an active laying of pheromones but can also derive from the incidental deposition of chemical cues. In this study, we investigated whether scent trails can influence path selection in the cockroach Blattella germanica (L.). Experiments were designed to separate the role of prior experience based on the orientation of the path and the presence of trails. In a first phase, cockroaches were able to access freely one or two branches of a platform during a 48 h period. In a second phase, cockroaches were offered a binary choice between one marked and one clean branch, or between two clean branches. In the absence of trails, cockroaches prefer the novel orientation but in the presence of a trail previously laid by the same group of individuals, they prefer the path with the trail, irrespective of orientation. However, cockroaches tended to avoid trails laid by a different group of cockroaches. Overall, our results indicate that both scent cues and response to novelty influence, weakly but significantly, path selection in cockroaches. The plausible nature of scent marks used by cockroaches is discussed. Our study suggests that the influence of incident trailing cues can be modulated by learning to support a flexible orientation strategy depending on individual experience.