Darwin called these plants the "the most wonderful in the world."
"Everyone loves carnivorous plants," said Aaron Ellison, a senior research fellow at Harvard Forest (the university's ecological research area) and an expert in killer flora.
The biggest, he said, may be the endangered Nepenthes rajah of Borneo. "It could eat a good-sized rat or small mammal."
Insects and other prey are lured by the plant's scent, but slip off the waxy surface into the pitcher-shaped centre and are consumed by the plant's digestive fluids.
Possibly the biggest carnivorous plant is Nepenthes rajah, pictured in Malaysia's Kinabalu National Park [Image: Minden Pictures, Corbis]
Ellison recommends looking at Wikipedia photos of the tubular plants, including the record holder, which measured 41 centimetres long. "That's a foot and change, so it can hold up to a gallon of water," he said.
In contrast, "the biggest ones we have here [in the U.S.] couldn't eat anything bigger than a small salamander."
Ellison studies a species of New England pitcher plant, Sarracenia purpurea.
Just like in our stomachs or cows' stomachs, the inside of a pitcher plant has a whole staff of micro-organisms that help it digest its food, he said.
Bacteria, protozoa, and mosquito and midge larvae all help the plant to get the nutrients it needs, so the bowl- or pitcher-shaped part of the plant can really be thought of as a little belly.
But what's the creepiest fate of things that fall into the belly—or "jaws"—of these botanical beasties?
"Oh, my ... They're all so good," Ellison said, but finally settled on the prey of the bladderwort, a genus of more than 200 species that have been described as "a better mousetrap," Ellison says.
Bladderworts, which live in freshwater environments, have tiny bladders, each with "a little vacuum of air under the water with two little hairs outside of it," which a tiny crustacean or copepod will think is prey.
A valve opens up and whoosh! The animal is trapped inside, and "the first thing the plant does is it pumps all the water out, and so now [the prey] is essentially drowning in air," he said.
"That's a pretty nasty one."
There's no pleasant way to die in a carnivorous plant, but one bug has gotten wise and is outsmarting the pitchers.
The diving ant (Camponotus schmitzi) has learned to swim inside some Asian pitcher plants and steal some of the sludge—and possibly other decomposing ants—for food.
"Evolution is always working in strange ways," Ellison said.