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A sophisticated system of vibrational long distance alarm communication was found in the African fungus growing termites Macrotermes bellicosus and M. subhyalinus. When disturbed in their nests and in their extended gallery systems, soldiers produce vibrational signals by drumming their heads against the substratum. The drumming signals are trains of pulses of substrate vibrations with pulse repetition rates of 26 Hz in M. bellicosus and 13 Hz in M. subhyalinus. In both species, the carrier frequency was about 1000 Hz and the signal amplitudes about 0.5 m/s 2 (acceleration, RMS). By using artificial stimuli, we examined the characteristics of the stimuli that can elicit drumming behaviour, the termites' sensitivity to substrate vibrations, their reaction time to stimuli, and their ability to discriminate vibrations of different temporal structures. We also investigated the behavioural responses of termites to drumming signals and the mechanism of long distance propagation of drumming signals through the nest and foraging sites. We found that the soldiers are extremely sensitive to vibrations, responding to vibrations with amplitudes as small as 1-2 nm by drumming themselves. This behaviour leads to the propagation of the vibrational alarm through a chain of drumming soldiers, resulting in a retreat of the termites into their nest. The termites' system of social long distance communication seems to be unique in insects.

Cuticular hydrocarbons are among the prime candidates for nestmate recognition in social insects. We analyzed the variation of cuticular hydrocarbons in the termite species M. subhyalinus in West Africa (Comoë National Park) on a small spatial scale (< 1 km). We found considerable variation in the composition of cuticular hydrocarbons among colonies, with four distinct chemical phenotypes. Different phenotypes occurred within each of the four habitats. The difference between these phenotypes is primarily due to unsaturated compounds. A clear correlation between the difference of the hydrocarbon composition and the aggression between colonies was found. This correlation also holds in a multivariate analysis of genetic similarity (measured by AFLPs), morphometric distances (measured by Mahalanobis-distances). as well as geographic distances between colonies. In a more detailed analysis of the correlation between the composition of cuticular hydrocarbons and aggression, we found that no single compound is sufficient to explain variation in aggression between pairings of colonies. Thus, termites seem to use a bouquet of compounds. Multiple regression analysis suggested that many of these compounds are unsaturated hydrocarbons and, thus, may play a key role in colony recognition.