Free Darwin's Island by Steve Jones Page A

Carolinas: ‘This wonderful plant seems to be distinguished in the creation, by the Author of nature, with faculties eminently superior to every other vegetable production . . . We see here, in this plant, motion and volition.’ The ‘irritable principle in vegetables’ was much commented on even if some denied that any plant would lower itself to prey on an animal. Linnaeus, the great classifier, insisted that the flytrap always let its prisoners go, while others claimed that the insects trapped within were sheltering from frogs. It even became part of legal philosophy. The social theorist Cesare Lombroso, who believed that crime was a biological throwback beyond the control of those responsible, felt that flytraps marked ‘the dawn of criminality’. They ‘establish that premeditation, ambush, killing for greed, and, to a certain extent, decision-making (refusing to kill insects that are too small) are derived completely from histology or the microstructure of organic tissue - and not from an alleged will.’
    The flytrap - and just a single species is known - lives in nitrogen-poor swamps in the Carolinas, its native home. It was given the erroneous Latin tag of Dionaea muscipula (which means ‘mouse-eater’ rather than ‘fly-eater’ as intended). Its popular name among the colonists was ‘tipitiwitchet’, then a slang term for female genitalia, because of its supposed resemblance to that organ, (although to avoid vulgarity Thomas Jefferson used the label ‘Aphrodite’s mousetrap’ when he added his specimen to his collection). Each bears up to a dozen traps, each made of a much-modified leaf. Darwin himself considered the creature to be ‘one of the most wonderful in the world’. Its trap closed on its prey with spines that interlocked like the teeth of a rat-trap, rather than gluing them to its leaves, but its sensitivity reminded him of the sundew’s quite different strategy.
    Just two snap-traps are known: the Venus flytrap itself, and the so-called waterwheel plant (again just a single species, but found scattered across the world) which does the same under water, on a smaller scale.
    Other freshwater flesh-eaters use another method: a lobster pot, a snare with a one-way entrance valve. A separate group, found both on land and in fresh water, has tiny capsules or bladders that, when touched, suck in prey with irresistible force.
    The bladderworts, as they are called, have hundreds of species, found everywhere except in Antarctica. They prime their trap by pumping water out across its wall. Another kind found on moist rocks in South America and parts of Africa specialises in single-celled animals, protozoa that swim into tiny slits in its specialised underground leaves. It shows a microscopic kind of carnivory and Darwin had speculated that it was indeed a meat-eater, although he had no idea of its food.
    The insect-killers of Roraima use a different trick, a pitfall based on rolled leaves with margins sealed together. The fatal ambush is covered with a slippery glaze and decorated with a nectar bait. The sixteen species known from that peak are relatives of heathers and their mountain allies. Some are a metre tall, some tiny. Other pitcher plants of the New and Old Worlds and of Australia also use rolled-up leaves to snare their prey and some are big enough to take mice. They come from quite a different section of the botanical kingdom. Their capital is in the New World, which has more of those baleful creatures than anywhere else. The cobra lily of the western United States has a mouth said to resemble that of a snake. It feasts on ants. Others among its kin have a flared cover that shelters the jaws of the trap and keeps water out. A different group with the same general appearance, the monkey cups from around the Indian Ocean, make their pitfalls as structures that spring from a leaf ’s mid-rib and are held at the end of a long tendril. They get their taxonomic name, Nepenthes , from the