Dr. Mario Pahl and colleagues review the main studies on the ability of insects to perceive number, and discuss the possible mechanisms involved in number recognition.
Recent behavioral investigations have shown that several invertebrate species (animals without backbones) share various numerical activities with bigger animals, such as birds and mammals.
This is because the ability to assess the number of food items, competitors or mates can help animals – even smaller ones like insects – to make better decisions when competing for resources or sexual partners.
For example, male mealworm beetles take into account the number of female and male beetles around them, when deciding on a strategy to guard their mates. Social insects such as bees and ants use numerical information when travelling outside the nest or hive. Honeybees make use of the number of landmarks on the way to a food source to find their way, and can discriminate between images based on the number of displayed objects.
When bumblebees forage on flowers with a constant number of 5 nectaries, they avoid revisiting an already depleted nectary by leaving the flower after exactly 5 probings. Such studies clearly demonstrate that there is a continuum of abilities between the so-called 'higher' and 'lower' animals.