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Bees have been observed grooming hurt body parts, which may indicate that they feel pain. Many injured insects continue to feed and mate unbothered when they are wounded, which had previously led researchers to assume that insects don’t feel pain.

“This [grooming] in itself is not direct evidence for pain,” says at Queen Mary University of London. “But it’s an important dent in the argument that insects obviously don’t feel pain.”

A creature might be able to objectively process hurtful stimuli in its brain – called “nociception”, the perception of something noxious – without necessarily experiencing a subjective, unpleasant feeling of pain. However, measuring the latter is tricky. After all, researchers cannot ask an animal to communicate what it feels.

Instead, Chittka’s team looked at whether buff-tailed bumblebees (Bombus terrestris) responded to a painful stimulus by grooming the sites of their wounds. The researchers divided 82 bees into three groups. One group received a touch on one of their antennae with a soldering iron heated to 65°C (149°F), while another group was prodded on the antenna with an unheated iron. The third set wasn’t poked at all. In the 2 minutes following the burn, the scorched insects groomed and tended to their antenna more often, and for longer, than the other groups.

“It’s a very strong difference,” says Chittka. “No subtlety at all.”

The finding is part of a growing body of research indicating that insects can feel emotions. It builds on Chittka’s previous studies suggesting that bumblebees will only in exchange for a particularly sugary reward, and that they might feel enjoyment because they freely engage in play.

“This study provides an important part of the overall picture,” says at the University of Southampton in the UK. Her team has developed a set of eight criteria for assessing whether an animal experiences pain, and this research addresses one of the conditions, she says.

Other scientists are less persuaded. at the London School of Economics says grooming an injury could simply be an evolved response intended to mitigate long-term damage, not a sign of pain. “We could think of it as a continuation of the immune response to tissue damage, which is nearly universal in animals,” he says. For example, a frog will vigorously wipe its skin to remove acid, and it maintains this behaviour even after its brain – and thus its potential ability to feel pain – has been destroyed.

Bees respond to afflictions more like sophisticated robots than like tiny humans, says at Dalhousie University in Canada. The nociceptive signal goes to the nervous system and gets processed, which can then alter the animal’s behaviour to avoid that stimulus in future. This can look like pain, says Adamo, but it’s similar to what robots can do to avoid damage. And insect brains don’t show anatomical evidence of neurons allocated for the emotional experience of pain – or other feelings.

“No one has found an emotional centre,” says Adamo. “Is it pain if it doesn’t hurt? I don’t know.”