The response to vibrations of the substrate and reactions to the specific drumming in colonies of carpenter ants (Camponotus,Formicidae, Hymenoptera)

1.	The physical characteristics of the drumming signal produced by workers of carpenter ants (Camponotus herculeanus L.) inside their nests, constructed in trees, were investigated. Typical elements of the inner nest structure are lamellae of about 50–500 cm2 derived from gnawing out the soft spring wood. On the thinnest lamellae (about 1 mm thick) the highest acceleration amplitudes of the signal were measured (on average 375 cm/s2 from peak to peak). The largest part of the intensity spectrum is between 200 and 1,500 Hz. On thicker lamellae the acceleration amplitudes are lower (at 12 mm thickness they average 140 cm/s2), and the upper end of the frequency range of the intensity spectrum is increased. The attenuation during the transmission is least along the longitudinal axis of thin cantilever lamellae (0.4 dB/cm) without alterations of thickness or connections to other lamellae. On a typical structure of the inner nest the attenuation is 1.2 dB/cm in the longitudinal axis, 2.7 dB/cm in the tangential axis and 4.3 dB/cm in the radial axis.
2.	The frequency of behavioural reactions to some vibrational stimuli was investigated. In worker ants sine-wave pulses release a stop-reaction (total freezing) or several reactions combined with locomotion (run-reactions). At high intensities (500 cm/s2) and high frequencies (1,000 Hz) mostly run-reactions occur, whereas, at the lower ranges, the stop-reaction predominates. The stop-reaction is released more often if the rise-decay times of the sine-wave pulses are short. The lowest acceleration threshold of reactions is 5 cm/s2 at frequencies ranging between 250–750 Hz. Stimulation with shockpulses causes mostly the stop-reaction and only few run-reactions. The lowest threshold is 5 cm/s2. Thus the animals can perceive the drumming signal over an average distance, depending on the direction of transmission, of 10–30 cm, and over 90 cm at the maximum. Shockpulse series are a stronger stimulus than single pulses of the same acceleration amplitude. The most effective time interval of the shockpulses is about 50 ms, which is the most frequent time interval of the beats of the natural drumming. A simple model describes the increased effect of shockpulse series by an additive superposition of functions of residual effects following the single pulses.
3.	Collective behavioural reactions to imitated drumming signals were investigated. They depend on the situation of the perceiving animals. The locomotory activity, measured by the number of changes from one nest compartment to the next, is increased by the signal. The combination with a second stimulus (air-puffs) increases the locomotory activity even more, and at the intensities used, multiplies the effects of the different stimuli. No orientation of the reactions with respect to the vibration source was found. The drumming signal shortens the time which males, females or larvae need to depart or to be carried by worker ants from nest areas affected by light to darkened ones. If ants of other species intrude into a nest, they are attacked more often. The drumming signal is not involved in the coordination of the mating flight.