Without legs or much of a face, ant larvae don’t have many options for expression. They can sway, however, and when they do, they’re signaling to their nursemaids that they want food, according to the most detailed study yet of body language in ant larvae.
Researchers have long observed swaying by larvae of many ant species. And a 2003 study showed a positive correlation between a larva’s motion and getting a meal.
More details have emerged in a study of the tropical ant Gnamptogenys striatula by Bruno Gobin of RSF-Royal Research Station of Gorsem in Sint-Truiden, Belgium, and his colleagues.
They fastened down an ant delicacy, a mealworm, outside a lab colony’s nursery so that nursemaid ants couldn’t drag it home but had to carry their larval charges out to dinner. This arrangement made it easier for the researchers to keep track of which larvae were being chosen for feeding. Videotapes confirmed that those larvae were that swayed more inside the nursery were more likely to be carried out to feed. In a separate experiment, the researchers held back food at times and found that deprived larvae swayed more than well-fed ones.
To look for the long-term benefits of a feed-me signal, Gobin’s group pampered some larvae with all-you-can-eat crickets and fruit flies but fed others only twice a week. Most of the well-fed young grew four reproductive organs called ovarioles, compared with only two for the less-pampered ants. In this species, the more organs a worker has, the better her chance of becoming one of the colony’s reproductive females, note Gobin and his colleagues in the February Animal Behaviour.