People did not ask this question about invertebrates like bees and snails fifty years ago:

Decades ago, scientists and lawmakers had all but reached a consensus that invertebrates could not feel pain, let alone other emotions like joy or fear. Recently, however, evidence is mounting that invertebrates are more than just reflexive beings. Experiments in bees, crabs, and octopuses show that some invertebrate animals can learn from painful experiences, have positive and negative emotion-like states, and might even experience a range of other emotions beyond pain and pleasure. But not all scientists agree that invertebrates feel anything analogous to vertebrate—much less human—emotion.

Natalie Mesa, “Do Invertebrates Have Emotions?” at The Scientist (May 26, 2022)

Assessing the evidence is tricky. In recent years, we have discovered that some invertebrates — octopuses, squid, and cuttlefish, for example — are much more intelligent than we used to think. That’s also true to some extent of lobsters and crabs. But they are special cases. Many other invertebrates, like clams, show little sign of cognitive awareness.

As Mesa goes on to note, it is hard to tell without skilful research. Many invertebrates do not have “faces” and their brains are organized very differently from ours. And, bluntly, some invertebrate behavior does not point in the direction of much sentience. As she observes, “Locusts continue to chew leaves as they’re being consumed by predators, and many insects don’t limp in response to injury.” Then there’s the praying mantis:

Eric Cassell, author of Animal Algorithms (2021), and entomologist Deborah M. Gordon describe the behavior of insects like ants as algorithmic, like that of a computer — which means that they probably aren’t “feeling” anything.

Other researchers alsoremain skeptical about pain in insects — and crustaceans:

Karen Mesce, a neuroscientist at the University of Minnesota, points out that crustaceans—like insects—lack the nervous system structures that allow humans and vertebrates to feel pain. In humans, pain and fear are processed in the amygdala and the limbic cortex, which the brains of crustaceans and insects lack. Human brains “have these special structures so that we can recall a heightened sense of whether things are good and bad,” she says.

Natalie Mesa, “Do Invertebrates Have Emotions?” at The Scientist (May 26, 2022)

Of course, it may turn out that some of the smarter invertebrates have equivalent — though not similar — structures to ours. At any rate, most researchers will concede pain in otherwise clearly intelligent cephalopods (octopuses, squid, and cuttlefish), if not insects:

The research question is really a bid for more humane treatment of intelligent invertebrates in industry. As Mesa notes, primatologist Frans de Waal and philosophy professor Kristin Andrews make the case for invertebrate emotions in a recent paper at Science. Here’s the Abstract:

If the UK joins a handful of other nations to recognize the sentience of invertebrates, such as cephalopod mollusks and decapod crustaceans, by, for example, prohibiting the boiling of live lobsters, this will be based on evidence that emotions and felt experiences (i.e., sentience) are not limited to animals close to humans, such as the mammals. This topic has been heavily debated in both affective neuroscience (how to define an emotion?) and philosophy (what is the moral relevance of animal experiences?), but a consensus on the criteria for and implications of recognizing animal sentience seems to be emerging.

Frans B. M. De Waal and Kristin Andrews, The question of animal emotions, Science, 24 Mar 2022, Vol 375, Issue 6587, pp. 1351-1352 DOI: 10.1126/science.abo2378 The paper requires a fee or subscription.

What we are learning is that invertebrate status is not, by itself, evidence of an inability to think or feel — as we used to suppose. However, just as vertebrates differ greatly in intelligence and sentience, invertebrates may differ greatly too. It’s early days yet for research.

You may also wish to read:

Researchers ask—serious question — do crabs have emotions?Recent research has created some unexpected ethical problems for the seafood industry. There are no simple answers to why some invertebrates show more intelligence and emotion than we would expect.

How could we know if an octopus or lobster felt pain? Researchers found that, when it comes to awareness, octopuses were the stars, followed by lobsters, crayfish, crabs, etc. How a life form acquires the ability to make intelligent decisions (and feel pain) is a fruitful mystery but it might blow up some assumptions about evolution.

and

Can crabs think? Can lobsters feel? What we know now. In Switzerland, it is now illegal to boil a lobster alive. Are the Swiss right? Is it cruel? How does a self that feels pain come to exist? And how do we distinguish information use — computer style — from self-awareness?