Ant antennae are both receivers and broadcasters, according to a new study from researchers at the University of Melbourne.
"An ant's antennae are their chief sensory organs, but until now we never knew that they could also be used to send out information," said the study's lead author, PhD student Qike Wang, in a press release.
The antennae, the scientists found, conveys information about which nest an ant comes from, telling other ants whether they are friend or foe.
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To figure that out, Wang and his team studied hundreds of ants, focusing on cuticular hydrocarbons (CHCs), a wax-like substance covering the bodies of ants, bees, flies and other insects that helps them avoid becoming dehydrated and is also a key to chemical communication.
The scientists observed that when they removed CHCs from only the antennae of an ant, leaving all other CHCs on the body intact, the non-nest-mates of the altered ant were not aggressive toward it, suggesting that the CHC-less ant's "friend or foe" information was missing.
Thus, the researchers reasoned, the CHCs on the antennae serve particularly as a kind of beacon broadcasting an ant's colony identification.
"Like everyone else," Wang said, "we assumed that antennae were just receptors, but nature can still surprise us."
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In a statement, the researchers cited the work of entomologist Auguste Forel more than a century ago. Forel gathered four species of ant, removed their antennae entirely, and then watched them interact. The ants, which might otherwise have been expected to quarrel, grouped together peacefully.
"Forel's experiment told us about antennae being used to receive chemical signals, but our research suggests that they are also a source of chemical signals," said Wang.
The study has just been published in the journal Proceedings of the Royal Society of London B.