Evidence for sonic communication in the German cockroach (Dictyoptera : Blattellidae)

Our objective was to test the hypothesis that late-instar nymph, male, and (or) female German cockroaches, Blattella germanica (L.), use sonic signals for intraspecific communication. A digital-recording system was assembled that consisted of a computer equipped with data-acquisition hardware and so ftware, microphones sensitive to sonic and ultrasonic frequencies, and spea kers capable of emitting sonic and ultrasonic sound. Sound was repeatedly r ecorded from groups of five nymphs, five virgin males, or five virgin femal es. Click-type sounds were commonly present in recordings from nymphs, and consisted of sound pulses of about 10-ms duration and peak frequencies of 7 , 9, 11, and 14 kHz. Similar "clicks" were found in recordings from females . In replicated binary choice arena bioassays with individual laboratory-re ared insects, played-back "clicks" from nymphs or females or computer-gener ated artificial clicks attracted nymphs but not males or females. These res ults provide the first evidence that sonic signals are part of the complex B. germanica communication system.