| Abstract: | ABSTRACT. Tracks of dewinged gypsy moth males, Lymantria dispar L. (Lymantriidae), walking upwind in an airstream without pheromone consist of marked alternations between more or less straight upwind segments, partly with an arcadic structure, and twisted segments. This apparently complicated behaviour can, however, simply be explained by a superposition of noise and two turning commands: an upwind turning tendency, derived from the anemoreceptive system, which represents an average of the moth's angular positions over a period of time; and an internal turning tendency which consists of strong but brief bursts. These bursts are produced intermittently; successive bursts do not necessarily alternate polarity. Amputation of one antenna increases the probability of bursts towards the amputated side; therefore a separate burst source is postulated for each antenna. In the presence of the attractant pheromone (+)-disparlure, the anemotactic signal is weighted higher; twisted segments are, therefore, less pronounced.
There is a chemotropotactical component involved in the male's orientation. The tropotactical signal, dependent on the difference of odour concentration perceived by the left and right antenna, competes with the upwind turning tendency. |
