VIBRATIONAL ALARM COMMUNICATION IN THE DAMP-WOOD TERMITE ZOOTERMOPSIS-NEVADENSIS

Vibrational alarm communication was studied in the New World, damp-woo d termite Zootermopsis nevadensis (Isoptera: Termopsidae). Workers and soldiers react to disturbance such as sudden bright light or air curr ents by drumming their heads against the substratum. This drumming has been described as alarm signalling; its functional significance and p erception by the nest mates, however, remained unclear. In the present study we analysed spectral and temporal properties and absolute ampli tudes of the vibrational signals and used behavioural responses of the termites to determine the thresholds of the sense of vibration and to find out if and how the termites discriminate the conspecific alarm s ignals from the background noise. The drumming signals are trains of p ulses of vibrations of the substratum with a pulse repetition rate of about 20 Hz. The carrier frequency depends on the substratum; in the n ests studied it was in the range 1-3 kHz. The highest vibrational ampl itudes measured close to the signal emitters are usually about 10 m/s2 (acceleration, RMS). The threshold of the behavioural response is abo ut 1 m/s2 over a wide range of frequencies (10 Hz to 5 kHz), indicatin g that the termites can detect these signals as vibrations of the subs tratum. The animals respond preferentially to temporal patterns simila r those of the natural signals; temporal rather than spectral cues see m to be used for signal discrimination.