We study how male American cockroaches, Periplaneta americana, track a plume of female pheromone upwind to its source. The cockroaches generate a walking track that appears quite similar to what we observe from the moths, however they may be using different mechanisms to control their steering manuevers. Because cockroaches have such long antennae (longer than their bodies) they appear to be making at least some of their decisions to turn by comparing the amount of odor detected by one antenna to that detected by the other. This is more easily seen at the boundary between the pheromone plume and clean air along the time-averaged edge of the plume.
Our experimental manipulations to date have included exposing males to: 1) different combinations of wind and odor, 2) four different pheromone structures 3) the removal of wind or odor half-way through their odor tracking, and 4) an obstacle in their path to the source. From these experiments we have learned that: 1) male cockroaches appear to have a "preferred" orientation to the wind direction and that their preference changes in the presence of pheromone, 2) they generate tracks of different structure when tracking plumes of different structures, 3) plume tracking is not significantly disrupted by the removal of wind, and 4) approximately 50% of males can alter their tracking behavior to negotiate an obstacle in the plume but the other 50% cannot.
Since the roaches' antennae are so long and are actively moved by the animal during tracking behavior, we have also measured their movements and analyzed the differences in antennal behaviors of the cockroaches in all of the above experiments. [Note: In the stick figures in the videos the insect is moving upwind from right to left, the body axis is represented by the black line, the green dot represents the head, and the red and blue lines represent the left and right antenna respectively.]
Video (overhead view) of the cockroaches tracking an odor plume (the time averaged plume boundary is represented by the red lines) upwind in our wind tunnel to the odor source. The wind is moving from left to right. Note the stereotypical zigzagging behavior similar to that seen in our moths. Now, when an aluminum meshlike obstacle is placed in the same arena (purple), the cockroach (red) has much more difficulty locating the odor source.