The Linear Track Olfactometer : An Assay Device for Taxes of the German Cockroach, Blattella germanica (L.)(Dictyoptera : Blattellidae) toward Their Aggregation Pheromone

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A T-shaped wind-tunnel olfactometer with a special wire pathway was designed and built to examine taxes of the German cockroach, Blattella germanica (L.) toward aggregation pheromonally odoured air or air current. Test animals were made to climb up to a T-junction on the wire and to choose a direction at one point. Chemotaxis and odour modulated anemotaxis were demonstrated in two different air-flow modes (C-mode and A-mode), respectively. Their shelter contaminated with their frass induced strong positive taxis in both modes in B. germanica nymphs. The preference toward the odour source was independent of the wind speed in the C-mode, whereas it correspondingly ascended with the increase of wind speed in the A-mode. The probit analysis on the excess proportion index and wind speed gave 0.86 cm/sec as the median effective stimulus level. Bilaterally antennectomized nymphs exhibited neither taxis, whereas those unilaterally antennectomized represented significant positive taxis toward the stimulus in both modes. The latter implied that besides tropotaxis, klinotaxis also participated in their orientation behaviour in both modes.