Do insects feel pain? Crickets certainly seem to, according to new research which finds they stroke and groom a sore antenna in much the same way as a dog nurses its hurt paw.<\/p>\n
Associate Prof Thomas White, an entomologist from the University of Sydney, said the experience of pain was a \u201clonger, drawn-out, ouchy feeling\u201d, that differed from a hardwired nerve response.<\/p>\n
But evidence for pain is difficult to establish in other species, he says, so scientists look for behavioural cues. One indicator is \u201cflexible self-protection\u201d, where an animal directs protection to a particular body part over an extended period of time.<\/p>\n
\u201cYou see a dog, limping, or licking its paw, or holding one particular arm \u2013 of course, we\u2019d immediately say, \u2018well that\u2019s in pain, it must be sore\u2019.\u201d Scientists search for evidence of similar responses to ascribe pain to other animals, including insects.<\/p>\n
So, to test the idea in crickets, researchers first had to give them an \u201couchy\u201d.<\/p>\n
In the study, published in Proceedings of the Royal Society, dozens of crickets were randomly selected to receive one of three treatments. Some had a heated soldering iron applied to one antenna, while other crickets received the same probe; unheated, and a third acted as a control.<\/p>\n
The soldering iron was set to 65C \u2013 hot enough to be a \u201cbit unpleasant\u201d, without causing lasting harm, White says.<\/p>\n
Crickets that received the hot probe \u201coverwhelmingly\u201d directed their attention to the affected antenna \u2013 they groomed it more frequently, and tended to it over a longer period of time, he says. \u201cThey weren\u2019t just agitated and flustered. They were directing their attention to the actual antennae that was hit with this hot probe.\u201d<\/p>\n
The other crickets? They were a bit perturbed, he says, but resumed normal activity very, very quickly.<\/p>\n
White says the behavioural responses would be immediately recognisable to us as pain, if we observed them in our pets or friends. \u201cWhich raises the question, why don\u2019t we make the same inference here?\u201d The answer, he says, has to do with human history, culture and insects\u2019 lack of similarity to us.<\/p>\n
Crickets that came into contact with a hot probe \u2018overwhelmingly\u2019 directed their attention to the affected antenna, according to a study Photograph: Obed Guayamiz Culqui\/Getty Images<\/p>\n
Science is slowly moving the dial, and revealing more and more about insect brains, behaviour and experiences.<\/p>\n
\u201cThese aren\u2019t just little machines,\u201d says White. \u201cThey have rich capabilities to learn, to make complex decisions and trade-offs.\u201d<\/p>\n
Studies have shown bumblebees engage in play-like<\/a> behaviour by rolling coloured wooden balls, while stressed bees show signs<\/a> of pessimism.<\/p>\n The New York Declaration on Animal Consciousness<\/a>, signed by more than 500 leading scientists and philosophers, acknowledges a \u201crealistic possibility of conscious experience\u201d in all vertebrates and many invertebrates, including insects.<\/p>\n Animal welfare laws are catching up, with some countries recognising sentience in invertebrates like cephalopods and crustaceans<\/a>.<\/p>\n Associate Prof Kate Umbers from Western Sydney University, and the managing director of Invertebrates Australia, says it makes sense that insects could be next. \u201cEvolutionarily speaking, insects are a crustacean on land, they share a common ancestor.\u201d<\/p>\n People underestimate insects \u201call the time\u201d, says Umbers, who was not involved in the study. \u201cHumans are notoriously not very good at appreciating things that are different from them.\u201d<\/p>\n