Ant colonies act like fortresses, protecting the bounty within from marauding invaders. Some animals have evolved blunt tools such as large claws to tear into the nests, but others have evolved far more subtle ways that allow them to wander into the colony uncontested. Called “myrmecophily” – literally “ant-love” – many species of insects and plants have evolved associations to live alongside ants, most of which are sympatric (where both species benefit), but some of which are parasitic (where only one benefits at the expense of the other).
One such parasitic association is with what are called ant nest beetles (Paussus). Ants communicate with each other through various complex mechanisms, mainly through smell, but also through sound. It was already known that the ant nest beetles were able to mimic their ant hosts' complex chemical signatures in order to infiltrate the colony. But new research has shown that once within the nest, they then use three different noises to copy the sounds of the different ant castes – workers, soldiers and queens – allowing them to live their whole lives with the nest, and even prey on the ants themselves without being caught.
“The use of highly sophisticated communication systems is the key attribute that enables ants to act as a superorganism, thereby facilitating their dominance of terrestrial ecosystems,” explain the authors in a new paper on the discovery that the beetles are able to copy the ants' noises, published in PLOS ONE. “That Paussus are able to prey upon brood and adults alike and interact with the queen without eliciting any aggressive behavior from the ants demonstrates the shear sophistication of their masquerade.”
This is not the first time that insects have been found to mimic the sounds of ants to gain acceptance. By making the noises of queens, caterpillars of the Maculinea rebeli butterfly are able to trick their host into thinking that they’re royalty; the ants then feed the caterpillars up until they’re ready to pupate. But this is the first time that such a mechanism has been found in beetles, and by far the most sophisticated as yet described for any ant parasite.
The ant nest beetle Paussus is seen on the right, surrounded by its host ants. Credit: ©Prof. Andrea Di Giulio
By rubbing a row of scrapers along ridges located near their back legs, technically called stridulation, the beetles are able to alter the pulse length and frequency of their noises to copy those produced by the different ant castes. In a series of experiments, the researchers were able to show that these noises were fully accepted by all members of the colony.
“We show that Paussus favieri is not only able to mimic ants’ stridulations but can also 'speak' three different 'languages', each corresponding to sounds produced by different ant castes, including the queen, to direct host ant behaviors,” report the authors. “Given the large number of insects that live in ant nests as specialized parasites, we suspect that acoustic mimicry has evolved several times in different phylogenetic [or evolutionary] lineages.”
What happens though, if the beetles somehow get found out by their host ant speices? “Well, the ants are really agressive, and if they find out beetles that are unhealthy or not perfectly chemically or acoustically mimetic they immediately kill and feed on them,” explained Adnrea Di Giulio, who coauthored the paper, to IFLScience.
Main image: Tim Keppens/Flickr CC BY-NC-ND 2.0.