It goes by witch’s hair, strangleweed, devil’s gut, wizard’s net, and hellbine. And anyone who sees dodder vines in action will quickly understand why they’ve earned such dastardly, eldritch names. These parasitic plants emerge from the ground as a slender tendril, which sniffs around for chemicals released by potential hosts. When the tendril finds a target, it wraps itself around a stem, grows into it, and, like a vampire, begins to drain its fluids.

From one host, dodder vines can reach many more. In a still photo, a dodder infestation looks like someone has thrown spaghetti over a field or forest. But if you speed up the vines’ movements with a time-lapse camera, they resemble a mass of writhing serpents, thrashing about in their quest for more nutrients. By the time it’s finished, a single dodder vine can connect dozens, perhaps hundreds, of hosts. “In our lab, we could connect at least 100 soybean plants with a dodder seedling,” says Jianqiang Wu from the Chinese Academy of Sciences.

And that, unexpectedly, has its upsides.

Wu’s team has now found that dodder inadvertently wires plants together, allowing them to trade chemical messages that warn one another of attacks by insects.

Plants may seem like passive victims, ready to be easily consumed by hungry animals. But in reality, they actively defend themselves. They can produce defensive toxins when their leaves and stems are attacked. They can communicate with each other by releasing alarm chemicals into the air, which tell neighboring plants to boost their defenses, or which summon parasitic wasps that kill the leaf-eating insects. They can also release different alarm signals throughout their bodies, so that a single assaulted leaf can trigger defenses in every leaf, as well as in roots, stems, and more.