A European caterpillar can garner royal treatment from ants by mimicking the sound of their queen.
Ants of the species
Myrmica schencki can be fooled into carrying certain caterpillars into the colony nurseries where the fakers enjoy full care and five-star dining, and then turns into a Maculinea rebeli butterfly.
Chemical camouflage alone will let the caterpillars game their way into the ant colony. But, the rhythmic caterpillar purring has the effect of the queen ant’s noises.
M. rebeli caterpillars make a mini version of the
brrrrrr of a woodcock or snipe, Thomas says. Recent work has suggested that caterpillar noises may come from repeated muscle spasms. And when caterpillars become enclosed pupae, they make noises by rubbing a scraper, or plectrum, on their abdomen against a patch of fine grooves called a file. “Actually they can wriggle their abdomen quite a bit,” Thomas says.
A caterpillar has fooled ants into feeding it during the final stages before it turns into a large blue butterfly. Photo: Jeremy Thomas
Advances in miniature electronics made the new study possible. When playing the caterpillar recordings to an ant colony, workers reacted as they do to queen scratchings. Most distinctive was what Thomas describes as on-guard attendance.
Clustering around the speaker, worker ants stay motionless in a hunched-over posture with antennae out and jaws slightly open. Like an honor guard around a human queen, worker ants will maintain that pose for hours.
Queen-mimicry could explain the VIP treatment caterpillars receive in the ant colony. “Quite often they’re treated as superior beings,” Thomas says. In a crisis, worker ants rescue caterpillars before a regular ant brood. And in famine, workers will kill their own brood and feed it to the caterpillar.
Ref.: Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite. 2009. F. Barbero, et al. Science 323: 782–785.
