Termites use the vibrations produced when they chew into wood to decide which bits to eat, researchers have discovered.
They also seem to use the acoustic vibration signals to detect the presence of other species of termite on the same piece of wood, and to help control the development of immature workers into sexually-active breeders. These findings might be exploited to protect homes without using pesticides, say the Australian team.
Termites have a reputation as voracious, indiscriminate eaters. But this is not so, says Theodore Evans of CSIRO Entomology in Canberra, Australia. Species that share the same habitat will often each go for only particular sizes of wood, with some eating twigs, and others fallen trees – presumably to avoid competition.
But it has not been clear how the blind insects quickly determine the size of a piece of wood. The new work suggests they use vibration-sensing organs at the base of their antennae and on their legs.
“They detect the resonant frequency of the vibrations made as they chew into the wood,” Evans says. “But I assume they also use information from their jaws on the hardness of the wood, and their detection of various chemicals in wood, to identify the wood species. They probably put all these things together to work out how big the piece of wood is.”
The team studied worker drywood termites, Cryptotermes domesticus, which happily munch into wooden buildings.
They exposed the workers to blocks of pine wood of various lengths, and recorded the vibration frequencies made as they walked over and bit into the wood. These workers preferred to burrow into only the shortest, 20-millimetre-long blocks.
But by loudly playing back the 20mm vibration frequencies, the team could trick the termites into burrowing into much longer pieces. Playing frequencies initially produced from long blocks also stopped termites burrowing into their favoured shorter pieces.
King and queen
Evans also noticed an impact on the termites’ sexual development. Playing the vibration recordings reduced the number of workers that matured into the reproductive stage by half, on average.
In a natural setting, many vibrations would indicate the presence of lots of other workers in the vicinity. Since workers that develop into breeders must fight with each other until only one king and one queen are left, the signal could have suggested lots of potential competition, and quashed development, Evans says. This is the first time that vibration signals have been linked to reproductive development in insects.
In unpublished work, Evans has also found that drywood workers can use vibration information to detect other species on the same piece of wood. He put one small Cryptotermes termite at one end of a twig, and a large, aggressive species at the other. “And the large species tunnelled straight for the smaller. It’s amazing – like guided missiles,” he says.
“Now I would love to figure out if we could actually scare termites away from a house if we broadcast the right kind of signals – if we could effectively say that a big, bad, mean termite colony is already here, and you don’t want to come in.” Such signals could be played at a decibel level audible to termites but not to people, he says.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0408649102)