The sundew and the butterwort are really more remarkable than the pitcher plants; for although the traps they set to catch their prey are not so fine and attractive as the strangely shaped and gorgeously colored pitchers, the two modest-looking little marshland plants actually move to catch their victim, in much the same way as some of the lower animals do.
The butterwort closes over its prey very much as a sea-anemone does, and the curling tentacles of the sundew, as they bend over a, struggling fly, remind one of the way a starfish wraps its arms round the oyster, the whelk, or the mussel it has seized for its dinner, while it sucks the poor thing out of its shell.
Yet although the butterwort and the sundew move when they are excited in so marvellous a way, they move very slowly. The tentacles of the sundew move as slowly as the hands of a clock, while the butterwort takes an hour or more before it quite closes over its prize; and if it were not for the sticky stuff with which the leaves are smeared I am afraid both plants would often lose their dinner. They could certainly never move fast enough to catch such a quick, restless thing as a fly.
But all insect-catching plants are not so slow in their movements as the sundew and the butterwort. The sundew has an American cousin named "Venus's Fly-trap" which can move quite quickly. Each leaf of this active little plant is a perfect fly-trap, and is able to close in from ten to thirty seconds.
Venus's fly-trap grows wild only in the eastern parts of North America, and like other insect ogres is found only on damp boggy ground. Its leaves, like those of its English relative the sundew, are arranged in a rosette and lie more or less flat upon the ground, and from the center of the rosette a slender flower-stalk rises, bearing a cluster of pretty, pale flowers.
The leaves are about four inches long and are very curiously shaped, each one being divided into two distinct parts by a narrow waist. About the lower half of the leaf there is nothing remarkable; it is really a flat, broad leaf-stalk with a broad wing on either side, and looks like an ordinary leaf--it is the upper half which is the trap. This is roundish in shape, and divided by the midrib into two parts, which incline towards one another like the leaves of a half-open book, and round the edge of each half are from twelve to twenty long, pointed teeth.
Now the leaves of the fly-trap are not sticky to the touch like those of the sundew and round the edge of one without coming to any harm; but in the central part of each half of the blade are a cluster of rosy-red spots and three very stiff, bristly hairs, which stand up, not quite straight, but slanting upwards towards the edge of the leaf. If in its wanderings the insect happens to step ever so lightly on one of these hairs, the two halves of the leaf-blade instantly and swiftly close, shutting up the little creature within the trap. The long teeth on the edges of the leaf lock into one another like the fingers of clasped hands, and before it knows what is happening, the unfortunate insect finds itself a prisoner.
At first, when the two halves of the leaf close over the insect, they are slightly curved, forming a little hollow chamber, something like a bean in shape, But gradually the walls of the prison grow flatter. Slowly they press inwards, crushing and squeezing the poor little victim to bits, while at the same time an acid fluid is poured forth from the rosy glands to dissolve and digest it. Then, when its dinner has been quite crushed up, and all the soft parts dissolved, the leaf swallows the juice again, now enriched with all that was digestible in the insect-sucking it through the same little red mouths from which the acid juice was poured forth; and when the meal is finished and the leaf once more opens the glands are quite dry again. The six stiff hairs, which while the leaf was closed were bent down like the closed blades of a pocket knife, now spring up into position again, and the leaf is all ready to catch another fly.
Although the clever fly-trap is very quick to catch its dinner, it is not so quick in eating it, evidently considering it not a good thing to hurry-over a meal. From eight to fourteen days a leaf will remain closed while it is slowly sucking out the juices of its prey; sometimes even twenty days will pass before the leaf opens; and if its meal should happen to be an extra large one, and more than it can manage to digest, the leaf may never open again, but will die, from over-eating.
Sometimes, too, the plant is a little too quick in its anxiety to secure a large prize, such as an earwig or a long, wriggly millipede, and will clap its leaf shut before the creature is fairly caught, but is half in and half out of the trap. Then the astonished victim often wriggles its way out again, for the spiky teeth on the edge of the leaf are flexible and can be bent open by a strong, struggling animal, and so the plant loses its dinner. But small insects, such as flies and midges, never have the chance of escaping, for they are always well within the trap before they touch the hairs that cause it to close.
The Venus's fly-trap has a near relation living wholly in the water instead of on marshy ground. It flourishes in shallow ditches and little pools surrounded by reeds and rushes in South and Central Europe. It has no roots, but floats near the top of the water like the bladderwort, the long straggling stem growing at one end as it dies-away at the other.
The leafy traps of this little water plant are very much like those of Venus's fly-trap, but in addition to the sharp teeth round their edges the leaves are provided with several long projecting bristles, which give them a spiky appearance, and are useful in keeping off creatures that are too big to be caught and eaten. But such small water-folk as the larva of gnats, sprightly little water-fleas, and tiny water-snails swim easily enough between these guarding bristles, and as they lightly brush against the sensitive hairs on the leaf the trap closes, and--well--that is the last of those venturesome little water-folk.
The little prisoners may live for several days in their leafy cage, but they cannot get out, and when the trap opens again all that remains of them is an assortment of bristles, shells, rings of horny skin, and such indigestible parts of their anatomy.