抄録
Preference tests were carried out to examine the influence of contamination with different number of adult German cockroach, Blattella germanica, on the behavior of nymphs of the same species. The results revealed that the adult cockroach secreted not only aggregation pheromone, but also dispersion-inducing substance.Aggregation response of the nymphs was found to the filter paper that had been contaminated by 5 or 10 adult cockroaches in a 200-ml test beaker. Intensity of the aggregation increased according to the length of time of contamination.Whereas, repellency response of the nymphs was found with the filter paper thoroughly wetted by the larger number of 50 or 100 adult cockroaches in a beaker, on the inner wall of which clear droplets had been deposited by the cockroaches. Intensity of the repellency seemed to be increased with the degree of wetness of the paper, but reduced obviously when the discharges were removed from the mouth parts of the cockroaches. The clear droplets, or salivary secretions, were secreted from the mouth parts of the adult American cockroach, Periplaneta americana, as wel as the Cerman cockroach when they were seized or disturbed. The saliva of both cockroaches showed definite repellency against the nymphs of B. germanica.These results led us to the conclusion that the cockroaches secrete repellent(s) in the saliva, which would act as the chemical stimuli for dispersion from highly crowded area or for warning against their predators.
