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Although termites have a reputation for being indiscriminate eaters, they can in fact be quite choosy. Indeed, in addition to selecting for wood palatability and hardness, different species are known to favor particular sizes of wood--presumably as a way of avoiding competition with other termites. Exactly how they manage this sizing up has puzzled scientists, however: the creatures are blind, and they do not pace the dimensions of a piece of wood before tucking into it. New research suggests they may be assessing their options by listening.
Theodore A. Evans of the Commonwealth Scientific and Industrial Research Organization in Australia and his colleagues tested drywood termites (Cryptotermes domesticus) to see what factors influence their dining decisions. The researchers offered the insects wood blocks of varying sizes and recorded the sounds they made as they walked and chewed. When given this choice, the termites showed a preference for the smaller blocks. But when the scientists played the recorded vibrations into fresh blocks of identical size and offered them to a new group of termites, they discovered that the insects preferentially tunneled into samples with "small block" noises, even when the block was actually bigger.
Because worker termites listen by sensing vibrations through organs on their antennae and legs, the authors posit that the insects can utilize the resonant frequency of wood pieces when choosing their timber tidbits. In addition, it appears that the creatures can tell the difference between recordings of other termites and artificially generated signals, because they reacted differently to each. Specifically, more individuals remained as asexual workers (as opposed to maturing into reproductive adults) in groups exposed to natural vibrations compared to groups that listened to no sounds or artificial signals. The authors posit that the termites were fooled into believing the blocks contained more competition and were thus content to remain as helpers. The work is described in a paper published online this week by the Proceedings of the National Academy of Sciences.