Perhaps you’ve heard that millennials are obsessed with plants. For a long time I remained unimpressed, considering plants can’t make sound, attack robbers, or even move. But I was wrong. Plants can do something beyond the abilities of mere cats*, dogs, and birds: they secrete a chemical that makes the caterpillars that eat them eat each other instead.
It’s common for caterpillars to eat each other when they’re stressed out by the lack of food. (We’ve all been there.) But why would they start eating each other when the plant food is right in front of them? Answer: because of devious behavior control by plants.
When plants are attacked (read: eaten) they make themselves more toxic by activating a chemical called methyl jasmonate. Scientists sprayed tomato plants with methyl jasmonate to kick off these responses, then unleashed caterpillars on them.
Compared to an untreated plant, a high-dose plant had five times as much plant left behind because the caterpillars were turning on each other instead. The caterpillars on a treated tomato plant ate twice as many other caterpillars than the ones on a control plant. The darkest part: if a single caterpillar was placed in with a bunch of dead ones, it even ended up eating the corpses sooner. (The results were published online this week in the journal Nature Ecology & Evolution.)
There are some caveats: plants can’t be slow on the uptake. If the caterpillar is already eating the plant, releasing all the methyl jasmonate in the world isn’t going to save it. They have to start secreting it at least a day before the bugs descended.
Also, we’re still not sure how much activating methyl jasmonate hurts the plant itself. For example, it’s possible that releasing the chemical drains the plant and then it doesn’t grow as many tomatoes. It’s also unclear how realistic this is as a defense mechanism in practice. The scientists put eight caterpillars on a small plant, so there were plenty of caterpillars to eat. If there were only one or two around, maybe the caterpillar would continue munching on the plant after all.
The important thing, though, is that I have a newfound respect for plants. In fact, I bought my first plant — a peace lily — just this weekend. I proudly texted a photo to my friend, who responded with: “a lily dies in Brooklyn.” I hope caterpillars strip all her plants bare before consuming each other until there is nothing left at all.
*To be fair, cats are full of mind-controlling parasites, which is cool, though owning one probably won’t give you mental illness.