Carnivorous Plants

Carnivorous plants

An insect getting trapped inside a carnivorous plant

Carnivorous plants are plants that attract, capture, and digest insects to obtain proteins and nutrients such as nitrogen. They are all green plants, and hence are able to make food for themselves.

They live in surroundings which are poor in some of the material they need to manufacture food, so they have learned to adapt to their environment by being able to supplement their food by capturing insects or other small animals. Some examples of carnivorous plants will be looked at in more detail below.



Among the common marsh plants are the bladderworts, so called because their bodies are kept afloat in water by means of numerous little bladders. While these bladders are used in this fashion, they also serve as most effective traps for certain very small water animals related to the insects.

Each bladder has a an opening which is guarded by a door like that of an ordinary rat trap. From the side of this entrance hairs float and wave about in the water, and within the transparent bladder are other waving tufts of hairs. These hairs are attractive to the minute water animals, and are pushed aside easily whilst entering the bladder. However escaping is impossible, for the door, which was easy to push aside on entering, cannot be moved outwards.

Pitcher plants

The giant plant trap can catch insects and small rodents in its pitcher shaped sack

Prominent among the carnivorous plants are the pitcher plants, whose leaves form tubes, or urns, or pitchers of various forms, which contain water, and to which insects are attracted and drowned.

The leaves are shaped like slender hollow cones, and rise in a tuft from the swampy ground. The mouth of this conical urn is over arched and shaded by a hood in which are translucent spots like small windows. Around the mouth of the urn are glands which secrete a sweet liquid, and drops of this nectar form a trail down the outside of the urn. Inside, just below the rim of the urn, is a glazed zone so smooth that insects cannot walk upon it.

Below the glazed zone is another zone thickly set with stiff downward-pointing hairs, and below this is the liquid in the bottom of the urn. If a fly is attracted by the nectar drops on this curious leaf, it naturally follows the trail up to the rim of the urn where the nectar is abundant. If it attempts to descend into the urn it slips on the glazed zone and falls into the water; and if it attempts to escape by crawling up the side of the urn, the thick-set, downward-pointing hairs prevent it. If it seeks to fly away from the rim it flies towards the translucent spots in the hood, which look like the way of escape, as the direction of entrance is in the shadow of the hood. Pounding against the hood the fly falls into the water.



Another group of carnivorous plants consists of the sun-dews which grow in swampy regions and are quite common in swamp areas. While the pitcher plants depend upon luring insects to their death by drowning, the sun-dews depend upon stickiness. The leaves form small rosettes on the ground and are of various shapes.

All of the plants glands secrete a clear sticky fluid which hangs to them in drops like dew drops, and since these dewdrops are not dispelled by the sun, the plants have been called the sun-dews, If a small insect, in flying or creeping across the plant, happens to touch one of the sticky drops it becomes entangled.

Venus fly-trap plants

Venus fly-trap

The most famous and remarkable of the fly-catching plants is the venus fly-trap, known only in swamps near Wilmington, North Carolina. This fly-trap does not depend upon drowning the insects, or upon sticking them fast, but upon its quickness of movement.

The lower part of the leaf is like any ordinary blade, but above becomes pinched almost in two, and then suddenly flares out again into a round blade-like expansion which is constructed like a steel trap, the two halves snapping together and the marginal bristles interlocking like the teeth of a trap. A few sensitive hair-like feelers are developed on the leaf surface, and when one of these is touched by a small flying or hovering insect, the trap snaps shut and the insect is caught.