The question of whether insects engage in play has long been a complex and controversial topic in the science of animal behavior, known as ethology. For decades, the answer was a clear no, based on the view that play requires a level of cognitive complexity absent in creatures with small brains. Recent observations, however, have challenged this conventional wisdom. These findings suggest that some insect species may exhibit behaviors that fit the formal scientific criteria for play, prompting scientists to reconsider the capacities of these tiny organisms.
Defining Play in Ethology
To classify a behavior as play, ethologists rely on a strict set of criteria that separate it from other activities like foraging or fighting. The first requirement is that the behavior must be non-functional, meaning it has no immediate purpose related to survival, such as gaining food or reproducing. Instead, it must be spontaneous and autotelic, meaning it is intrinsically rewarding to the animal.
Play is also characterized by its form, often appearing exaggerated, incomplete, or structurally different from its functional counterpart. For instance, mock fighting may involve inhibited movements that would never be used in a real conflict. Furthermore, true play must be repeated but not rigidly stereotyped, showing variability in its execution. Finally, the behavior must be initiated when the animal is in a safe, relaxed, and stress-free state, suggesting a surplus of energy and a non-urgent environment.
Explaining Behaviors That Look Like Play
Many insect actions that appear playful to human observers are traditionally explained by clear, survival-based functions. Behaviors like chasing, intricate flight patterns, or object manipulation are typically categorized as practice, territorial defense, or necessary exploration. The high-speed aerial pursuit seen in many fly species, for example, is not a game but a highly-tuned, visually-driven behavior used for mating or predation. The fly tracks a moving target with impressive accuracy.
Another common observation is the “wrestling” or dueling seen among some ants, such as the Indian jumping ant (Harpegnathos saltator). These physical interactions, which often involve antennal strikes, are not for fun but establish a shared dominance hierarchy within the colony. This ritualized aggression is a social strategy that determines which workers gain the ability to lay eggs, linking it directly to reproduction and colony structure. Exploratory movements are necessary for insects to map their environment and forage successfully, but these actions are goal-directed toward resource acquisition.
Specific Studies Challenging the Conventional View
The traditional scientific consensus has been challenged by recent laboratory observations that appear to meet the strict criteria for play behavior. A study on bumblebees (Bombus terrestris) provided the first documented evidence of object play in an insect. Researchers observed bees repeatedly rolling small wooden balls, an action that provided no food reward, did not aid in nest cleaning, and was not associated with mating.
Individual bees voluntarily engaged with the balls, sometimes up to 117 times, and they showed a preference for chambers where they had previously rolled them, suggesting the activity itself was intrinsically rewarding. The study also found that younger bees and adult males engaged in this behavior more often and for longer periods, which mirrors the age and sex patterns of playfulness seen in mammals and birds. Furthermore, studies on the vinegar fly (Drosophila melanogaster) have shown play-like behavior where flies voluntarily engaged with a rotating platform, or carousel, performing movements like swinging and bobbing. This active engagement with sensation, which was not necessary for survival, suggests that the capacity for self-rewarding, non-functional activity may be a feature of even relatively simple nervous systems.