Further characterization of a dispersion-inducing contact pheromone in the saliva of the German cockroach, Blattella germanica L. (Blattodea: Blattellidae)

The dispersion-inducing substance in the saliva of the German cockroach was characterized by different chemical extraction and precipitation procedures. The repellency factors of probe solutions were estimated by a computer-aided device analysing the pheromone-induced motility behaviour. The dispersion pheromone was perceived by contact only and remained active for at least 15 days. Saliva of males, nymphs, gravid and non-gravid females showed significant repellency, but in a quantitatively varying manner. Overcrowding procedures increased the dispersal activity of the saliva and the content of the 77, 80 and 82 kDalton (kDa) proteins in the saliva. Antagonism between the dispersal pheromone in the saliva and the aggregation pheromone in the faeces could be demonstrated herewith. Salivary proteins were detected to be the only source of the repellent activity. After characterization and fractionation of the salivary proteins by gel electrophoretic and HPLC-techniques it was shown that the dispersion-inducing behaviour was caused by the 77–82 kDa proteins. A strong linear correlation ( r = 0.914) between the applicated quantity of the 77–82 kDa proteins and the resulting repellency was calculated. Male German cockroaches perceiving a threshold quantity of 250 ng of the 77–82 kDa proteins/cm ² displayed typical dispersion behaviour. It is suggested that the dispersion-inducing proteins take effect in two different ways: 1. (1) as a defence pheromone of early nymphal stages deterring adult cockroaches from cannibalism; 2. (2) as a dispersion pheromone mainly emitted by females under stress-inducing conditions, thus acting as a regulator of space. In both cases, males presenting the strongest reaction are presumed to be the main target group for the pheromone.