Lurking amidst greenery, predatory plants lure animal victims to nightmarish deaths. Let the reader imagine an ordinary housefly buzzing across a meadow in springtime. It is happy because its sensors have detected what every fly dreams of: the seductive, pungent scent of flower nectar. Naturally, it has no idea that a passionate addiction to this nectar will soon bring its too brief life to a nightmarish end.
It goes skimming along just above the grass, with its bulging, multi-lens eyes peering about in search of the nectarbearing plant. Then suddenly there it is -- a funnel-shaped, foot-high pitcher plant, looming above like a skyscraper. At this close range the plant fairly drenches the fly's chemosensors in a heady fragrance of nectar, while delighting its eyes with brilliant maroon-and-yellow markings. In a fever of anticipation the fly swoops straight up to the lip of the plant's open mouth and begins edging toward the imagined reward, a lifetime supply of tasty nectar.Then abruptly, disaster sets in. Wandering a millimeter too far inside the lip, it finds itself slipping and sliding across the waxy-smooth, downward-sloping lining of the funnel's interior. Slick as an ice pond, the lining resists the fly's frantic efforts to dig in and stop its fall. Instead, it tumbles uncontrollably down the "ice slide," heading deep into the plant's interior, which looks like a bottomless elevator shaft. In a panic, it flails its legs and beats its wings, but nothing works: the shaft is lined with spearlike hairs that point downward. They allow the insect to slide past easily, but impale it if it attempts to struggle upward.
Then the nightmare reaches a climax in a scene out of Dante's Inferno. The fly plunges deep into a pool of thick liquid at the base of the pitcher plant. Floating in this cesspool are the decomposed bodies of hundreds of the plant's earlier victims, now melted down by natural rotting action and the corrosive effects of the pitcher plant's digestive enzyme juices. As the fly thrashes about desperately in this fetid, decaying brew, paralyzing fluids slowly eat into its body. Within a few minutes it sinks, lifeless, into the swill. Soon its body fluids begin leaking out into the common cesspool from which the plant withdraws nutrients at its leisure.
Carnivorous plants are not dark, hidden growths that an unwary insect will stumble onto. Animal-trapping plants are often a riot of color: brilliant reds, creamy whites, buttery yellows, lavenders, many shades of green and other striking hues.
The rich yellow funnel of a pitcher plant may be decorated with eye-catching maroon veins. All this coloration is a functional part of the plant's seductive apparatus. Pitcher plants, for example, make their living by reaching out with scents and colors to lure into their traps victims that would have otherwise passed them by, unharmed.
Sundew plants inflict another unpleasant fate on their victims. The upper surface of the leaf is peppered with short, stubby tentacles from which it secretes a glistening, sticky bubble of clear liquid. Shining in the sunlight, with rainbow color effects, the bubble looks like a dewdrop - to an insect it resembles a precious drop of nectar. A powerful fragrance is also secreted from the bubble that attracts insects from all directions. An eager insect, attracted by either the sight or the odor of the sundew, will drop down amid the bubbles and try to drink the "nectar" when it finds itself stuck fast. As it thrashes around to get free, the sundew leaf's outer edges slowly curl around the insect so that more of its digestive glands can partake of the feast.
The Venus' flytrap is a well-known but extraordinary species of carnivorous plant that has evolved an almost perfect trapping mechanism. At the end of the leaves are flaps that resemble two clam shell halves. Around its margins are numerous sturdy guard hairs, and the pale green trap lining changes to bright red near the center. The trap is normally open 45 to 60 degrees so that insects will be attracted by both the bright color and the alluring nectar secreted by the plant. The trap will not be activated unless an insect brushing against the sensitive trigger hairs touches two hairs or the same hair twice. Then the flaps spring closed and the spines interlock to imprison the victim -- all in about a half second. The two-hair fail-safe keeps the trap from being triggered by a windblown particle or a drop of rain landing on the open flap. Each of the 8-12 traps on a plant can carry out two catching processes before it dies.
Although we animals have for untold eons been nourished by the plant world, the idea that some plants capture, kill, and eat our distant relatives seems repugnant to many humans. We normally expect plants to transform sunlight, carbon dioxide, water and assorted minerals into all the nutrition they will ever need. But these essentials are not available everywhere. In wet, acidic soil deficient in nutrients that plants need to survive, living creatures are the most expedient source of the nourishment they require. Perhaps we are apprehensive that humans could also be on the menu for really large carnivorous plants. Fortunately, their prey is mostly insects and, despite turn-of-the-century tales of man-eating plants, no creature larger than a mouse or tiny snake is at risk from those mischievous, clever carnivorous vegetables.
Phil and Nancy Seff are the authors of several science books, including "Our Fascinating Earth." Their column runs regularly in the Deseret News Science/Technology section.