Plants that lure bugs with bugs so they’ll eat other bugs
From a human perspective, most plants are passive beings, growing quietly in the dirt, hoping not to be disturbed. Look a bit closer, and you’ll find that that’s not quite the case. Many plants actually have passive, active or in the case of a serpentine columbine, passive aggressive forms of defense.
The serpentine columbine, (Aquilegia eximia), has evolved an elaborate system of self-defense. It begins with innocuous looking hairs along the plant’s stem, called trichomes. The trichomes carry droplets of sticky liquid, which then snare insects crawling on the plant.
The trapped insects accumulate, acting as a lure for predatory bugs, such as spiders or assassin bugs. The predators can then enjoy the buffet, but for the columbine’s plan to work, they need to treat the captured bugs as an appetizer. The real target in all this are Heliothis phloxiphaga caterpillars, which eat the plant’s buds, flowers and fruit if left unchecked. With a hungry spider around, however, surveys have found that the caterpillar’s numbers are significantly diminished.
A floral mastermind
While this may seem like a nefarious scheme for what must surely be a sinister flower, the reduction of caterpillars could have still been coincidental. Researchers from UC Davis wanted to confirm that this really was a system and not just predators taking advantage of plants that may have been sticky for some other reason. To see if the serpentine columbine really had some agency in all this, they put clippings of the plant in mesh-covered dishes. The mesh would allow smells or other chemical agents to be detected by bugs, but the bugs wouldn’t be able to make contact with the trichomes.
Popular solution to pest control
They found that would-be bait bugs did seem to seek out the covered plants, indicating that some sort of chemical lure was being emitted by the plant. If not, the bugs wouldn’t have had any further reason to stick around as they weren’t stuck on the plant clippings in any way. This means that serpentine columbine really is the root of this elaborate setup, luring and capturing one set of bugs so that they can lure predators, in hopes that those predators will eat the caterpillars that were bothering the flower in the first place. While this system may seem overly complicated for its own good, it works well enough to possibly be used by around 110 other species of sticky, bug-capturing plants.
Source: Plants Murder Bugs to Pay Their Bodyguards by Elizabeth Preston, Inkfish