The plant that turns a window into a lethal weapon

One of the most annoy­ing sounds of sum­mer is Thunk! Not a single Thunk! but the repet­it­ive Thunk! Thunk! Thunk! of a fly repeatedly banging its head against a win­dow. It doesn’t mat­ter how much of a win­dow you leave open, there’s always a fly that will bang its head against the win­dow just for the joy of syn­co­pated rhythm. If that irrit­ates you as much as it does me, then you will love the cobra lily.

Cobra Lily

Cobra Lily, Darlingtonia cali­for­nica. Photo by Brent Miller/Flickr

The cobra lily, Darlingtonia cali­for­nica, doesn’t just have a cool name. It has win­dows, of a sort, and it uses them with deadly effect.

The name comes from the hood that the plant has. In the bot­tom of the hood is an open­ing and there’s a trail of nec­tar lead­ing up there. What hap­pens at the top? The prey tries to find a way out. You’d think the big hole in came in would make a per­fect way out. However, the plant is sneaky.

Parts of the hood are trans­lu­cent, so the sun can shine through. Those same genes that guide the fly back into a win­dow time and again are triggered by the plant. The insect will attempt to bang its head again the hood again and again to find a way out, ignor­ing the way it came in. After a while it tires, and then it becomes obvi­ous that the cobra lily isn’t a lily after all.

It’s a pitcher plant.

This video from The Carnivorous Plant Whisperer on YouTube explains how the trap works from the insect’s point of view.

…and here it is in action with a fly wan­der­ing into the hood.

The sound will still annoy me. Yet I will have some sat­is­fac­tion know­ing that some­thing is exploit­ing the fly’s habit.

Photo: Darlingtonia cali­for­nica (Sarraceniaceae); California pitcher-plant by Brent Miller. This image licensed under a Creative Commons by-nc-nd licence.

Alun Salt. ORCID 0000-0002-1261-4283

When he's not the web developer for AoB Blog, Alun Salt researches something that could be mistaken for the archaeology of science. His current research is about whether there's such a thing as scientific heritage and if there is how would you recognise it?