Quirks and Quarks

Plant bleeds nectar to recruit ant bodyguards

When beetles or slugs injure the plant, it releases nectar that summons predatory ants to its defence

Injuries from herbivorous insect release attractant that summons predators

Ant-attracting nectar secretion from the edge of a wound on a bittersweet nightshade leaf. (Tobias Lortzing)
Plants that have the capacity to close wounds, do so quickly, to prevent infection or the loss of valuable resources. But the bittersweet nightshade - a weed-like vine found throughout Europe and North America - does something different. 

A new study by Dr. Anke Steppuhn, a Professor from the Institute of Biology at the Free University in Berlin, has found that when the nightshade is wounded, or eaten, by flea beetles and slugs, instead of closing the wound, it produces a sugary nectar around the edges of the damaged area. The nectar attracts ants, who are hungry for a sugary treat. 

In this way, the nightshade has enlisted the ants to protect it, as they kill the slugs and eat the nutritious beetle larvae, preventing further damage. 

Related Links

Paper in Nature Plants
National Geographic story
- Phys.org story
- New Scientist story