Carnivorous Plants

Carnivorous plants are various types of flowering plants and fungi that capture and digest prey animals. Photosynthetic carnivorous plants live in habitats poor in minerals, and they benefit primarily from the mineral nutrients gained from the prey. Since the animals they capture are primarily arthropods and chiefly insects, canivorous plants are sometimes called insectivorous plants, or even vertebrates such as small frogs and birds. Carnivorousness has arisen independently  in several unrelated groups, and families once thought not to have carnivorous members have later been found to do so. More are likely to be found. Carnivorous plants may be grouped according to their trapping mechanisms (see table, which lists examples of eacht trap type), as well as according to the biological classification system.


Method of Capture
Trap types observed in carnivorous plants include pitfalls and "lobster traps", adhesive traps, and various kinds of mechanical traps.
Pitfalls exist in a number of unrelated groups of flowering plants. These traps consist of tubular leaves, or arrays of leaves, that are filled with water. Insects are captured when they fall into the fluid, which often contains wetting agents and digestive enzymes. So-called lobster pots also consist of tubular leaves. In this type of trap, however, the tube is often horizontal and is lined with hairs that guide the prey along a path leading to the digestive part of the trap. Bromeliads, of the pineapple family Bromeliaceae, may also be mentioned, because some have leaf bases that form definite cups in which water accumulates. Such plants do not trap insects, however, so much as simply make use of nutrients provided by dead vegetation and animal remains that fall into the cups.
Adhesive traps involve sticky surfaces. Sticky-haired adhesive traps exist in several plant families. Typically, flying insects are captured when they adhere to slime secreted by hairs covering the leaf. In some genera, such as Drosera, the leaf actively moves the prey to the center and wraps around it. Sticky-needed adhesive traps have only recently been observed but may be widespread. The seed of the shepherd's purse, capsera, a common lawn weed, attracts, captures, and utilizes nutrients from prey; soil bacteria do the digesting.
Mechanical traps of various types occur. So-called snap traps, including the Venus's-flytrap, are found in only one family, the sundew family. Droseraceae, and in only two genera, Dionaea and Aldrovanda, each with a single species. In these plants the prey is trapped by rapid closure of a set of lobes around the animal when it touches sensory hairs that trigger the closure. The action results from acid growth in the lobes within less than a second. Suction traps, found in the aquatic Bladderwort Ultricularia, are similar to the style of mouse trap in which a door allows the mouse to enter but not to exit. The prey trips a lever on the plant "door", which allows water and the prey to be sucked into the trap when the plant's concave side puffs outward. Snare traps are found in carnivorous fungi. One type, in the genus Arthobotrys, has a trap that looks like a small lasso with three segments around the loop. When triggered by a nematode, the segments bulge out to capture the worm. The fungus then grows into the prey and digests it.

Flowering carnivorous plants occur in freshwater, in Sphagnum (peat moss) bogs and other swampy areas, on trees and old logs, and on hardened soils that are seasonally very wet. Plants in seasonally wet areas have dormancy mechanisms that they use druing the dry periods. (An exception, Drosophyllum, which grows in dry areas in Portugal, is reported to have to have a deep taproot.) The features common to nearly all habitats of carnivorous plants include low levels of mineral nutrients, at least a periodic abudance of water, and bright sunlight. Trapping mechanism often involve loss of water from the leaf and are likely to decrease photosynthetic efficiency. In a mineral-poor environment, these tradeoffs are apparently worth the supplementary mineral nutrients gained.

Growing Conditions
Carnivorous plants grown indoors should be provided with bright light, a lot of water, and a medium (such as peat moss) that is low in minerals. Maintaining high humidity and watering with rainwater or distilled water is desirable. The plants should not be overfed or given meat, because meat contains too much salt. The plants can catch their own insects or be fed a few small ones each week.