According to entomologists, butterflies do not feel pain.
Although butterflies know when they are touched, their nervous system does not have pain receptors that registers pain as we know it.
I’ve seen caterpillars, chrysalises, and butterflies try to knock predators and parasitoids off their bodies. The idea that they would not feel ‘pain’ was one that I couldn’t understand until I watched dozens of butterflies that had lost their abdomens.
At our farm, we keep our breeding butterflies in screened gardens/rooms we call apartments.
After about ten years, mice started coming into the apartments in the winter. With food supplies low, they found butterflies to be an easy meal, living in the screened rooms, roosting on the screened walls, and easy to grab to eat. We would arrive at work to find mice droppings in the apartments. At first we weren’t sure why mice were going into the apartments unless it was to eat the fruit we had out for our butterflies.
We soon noticed that many of the butterflies, when they flew, would land and fall forward on their heads, straighten back up, and begin to eat. This was new strange behavior. A closer look revealed that the Monarch, Julia, and Buckeye butterflies were the ones with this problem. One to three dozen each morning would be missing abdomens. Without the normal weight of an abdomen, their balance was thrown off and when they landed, they’d tip over, straighten up, and begin to eat.
Yes, without abdomens, they ate as normal. They flew normal. They acted normal in every way. Males with abdomens would try to mate with females without abdomens, never realizing that the abdomen was missing.
Without abdomens, they would live for about 18 hours, flying, eating, and acting totally normal.
As we watched their behavior, we realized that they weren’t experiencing pain. They didn’t avoid other butterflies. They acted normal in every way except that their balance was a bit off when they landed. Like most people, we had to be convinced that they didn’t feel pain. Their own actions convinced us.
Since those years, we brought in Grandma Kitty and she takes care of the mice. Other than her leaving a gift at the door for us at times, this arrangement has worked out well. She is an old cat, not eager to run and play, climb screen walls and play with fluttering butterflies. As long as we feed her and stop to pet her often, she’s a happy cat. After the first winter with Grandma Kitty at the farm, our butterflies now keep their abdomens.
Of course we have to laugh when we see things like male butterflies drinking from an upchucked hairball, male Gulf Fritillary butterflies drinking from vomited cat food, and other (gross-to-humans) male butterfly behavior. Some of the side benefits of having a cat at a farm are hardly topics for the dining room table.