In fact, there's mounting evidence that insects can experience a remarkable range of feelings. They can be literally buzzing with delight at pleasant surprises, or sink into depression when bad things happen that are out of their control. They can be optimistic, cynical, or frightened, and respond to pain just like any mammal would. And though no one has yet identified a nostalgic mosquito, mortified ant, or sardonic cockroach, the apparent complexity of their feelings is growing every year.
When Scott Waddell, professor of neurobiology at the University of Oxford, first started working on emotions in fruit flies, he had a favourite running joke – "…that, you know, I wasn't intending on studying ambition", he says.
Fast-forward to today, and the concept of go-getting insects is not so outrageous as it once was. Waddell points out that some research has found that fruit flies do pay attention to what their peers are doing, and are able to learn from them.
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They're strikingly similar to other animals, and yet vividly different. Insects have many of the same organs as humans – with hearts, brains, intestines and ovaries or testicles – but lack lungs and stomachs. And instead of being hooked up to a network of blood vessels, the contents of their bodies float in a kind of soup, which delivers food and carries away waste. The whole lot is then encased in a hard shell, the exoskeleton, which is made of chitin, the same material fungi use to build their bodies.
The architecture of their brains follows a similar pattern. Insects don't have the exact same brain regions as vertebrates, but they do have areas that perform similar functions. For example, most learning and memory in insects relies on "mushroom bodies" – domed brain regions which have been compared to the cortex, the folded outer layer that's largely responsible for human intelligence, including thought and consciousness.
(Tantalisingly, even insect larvae have mushroom bodies, and some of the neurons within them remain for their whole lives – so it's been suggested that adult insects that went through this stage might be able to remember some things that happened before they metamorphosed.)
There's mounting evidence that our parallel neural setups power a number of shared cognitive abilities, too. Bees can count up to four. Cockroaches have rich social lives, and form tribes that stick together and communicate. Ants can even pioneer new tools – they can select suitable objects from their environment and apply them to a task they're trying to complete, like using sponges to carry honey back to their nest.
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In The Expression of the Emotions in Man and Animals, Darwin argues that – just like every other characteristic – the ways humans express their feelings would hardly have appeared out of nowhere in our own species. Instead, our facial expressions, actions and noises are likely to have evolved via a gradual process over millennia. Crucially, this means that there's probably some continuity among animals, in terms of the ways that we display our emotional state to others.
For example, Darwin noted that animals often make loud noises when they're excited. Among the loud chattering of storks and the threatening rattling of some snakes, he cites the "stridulations", or loud vibrations, of many insects, which they make when they're sexually aroused. Darwin also observed that bees change their hums when they're cross. This all suggests that you don't need to have a voice box to express how you're feeling.
Take the golden tortoise beetle, which looks like a miniature tortoise that's been dipped in molten gold. It's not actually covered in the element, but instead achieves its glamorous look by reflecting light off fluid-filled grooves embedded in its shell. However, pick one of these living jewels up – or stress it out in any way – and it will transform before your eyes, flushing ruby-red until it resembles a large iridescent ladybird.
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The discovery of insect emotions also poses a slightly awkward dilemma for researchers – especially those who have devoted their careers to uncovering them.
Fruit flies are the archetypal research animal, studied so intensively that researchers know more about them than almost any other. At the time of writing, there are around 762,000 scientific papers that mention its Latin name, "Drosophila melanogaster", on Google scholar. Equally, studies into bees are growing in popularity, for the insights they can provide into everything from epigenetics – the study of how the environment can influence the way our genes are expressed – to learning and memory. Both have endured more than their fair share of experimentation.
"I like to watch bees and I've studied behaviour for a lot of my career, so I empathise quite a lot with them already," says Wright, who has been a vegetarian for decades. However, the numbers used in research are tiny compared to those sacrificed elsewhere, so she feels that it’s easier to justify. "It's this sort of disregard of life in general that we have [that Wright finds more problematic] – you know, people just wantonly take life and destroy it and manipulate it … from humans to mammals, insects to plants."
But while using insects for research is still largely uncontroversial, the discovery that they may think and feel raises a number of sticky conundrums for other fields.
There's already a historical precedent for banning pesticides to protect certain insects – such as the EU-wide embargo on nicotinoids for the sake of bees. Could there be scope for moving away from others? And though insects are increasingly promoted as a noble and environmentally friendly alternative to meat from vertebrates, is this actually an ethical win? After all, you'd have to kill 975,225 grasshoppers to get the same volume of meat as you would from a single cow.
Perhaps one reason we don't tend to think of insects as emotional is that it would be overwhelming.
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