Abstract
Chemotaxis and anemotaxis of nymphs of the German cockroach, Blattella germanica (L.)to their aggregation pheromone were investigated in the linear track olfactometer at different doses. The chemotaxis response consistently increased in accordance with dose. Odour-modulated anemotaxis response was initiated simultaneously with chemotaxis, but had an optimum dose level and decreased at higher doses. This decrease may be the result of the transition to the pin-point local search using solely chemotaxis. In addition to absolute odour presentation of the standard chemotaxis experiment using clean control air, odorous air was also provided to the control, and nymphs were exposed to varying concecntrations. Comparison of results revealed that the nymphs sensed not only the presence or absence of the odour but variance within the odour concentration itself. They discriminated concentration ratios of at least 1 : 1.6.
