Insectivorous plant

“ Every plant has its insect enemy, or, more correctly, its insect lover, which feeds upon it, delights in its luxuriance, but makes short work, it may be of leaves, it may be of flowers, it may be of fruit. It has been estimated that every known species of plant has five or six species of insects which habitually feed upon it. ”

“ The enemies of growing things have certainly increased alarmingly of late years. I cannot recall that formerly any insect was to be found in either vegetable or flower garden, other than the potato bug, currant-worm, cabbage-worm, and the green worm and small black beetle on the Rose; but now there are so many horrid creatures lying in wait until a plant is in perfection, to cut the stalk, or eat the root, or eat the pith from the stalk so that it falls, or to devour the leaves and eat the blossoms, that insecticides and a spraying machine are as necessary to a garden as a spade. ”

“ These insects are not always content with the leaf, but attack the flower also: even this food is too gross for many; the bee, the butterfly, the moth, as well as several species of flies, feed only on the honey, or finer juices, which they collect from flowers. We are continually finding the larva of some insect in pears, plumbs, peaches, and other fruit; these unwelcome intruders on the produce of human industry divide fruits, grain, and corn with us, often depriving us of large quantities. There is, indeed, no part of a plant which does not serve as food to different insects ”

“ Sometimes house plants, and out-door plants as well, become covered with a small, green insect called the plant louse or aphis. This insect has a sharp beak like a mosquito and it sucks the juices from the leaf and causes it to curl up, interfering with its work and finally killing it. ”

“ There are two practical methods of combating insect enemies and diseases of plants; one is to so carefully cultivate and stimulate the growth of the plants that they may possess the power of resisting attack; the other is to make war directly upon them by artificial means. Of course, the first method is most applicable or practicable against the more minute species, such as the plant-lice, rust, smut, and mildew. I do not recommend forcing plants to extremes, in order to enable them to resist their enemies, as this might work an irreparable injury ”

“ As certain insects prey upon plants or rob them of their nectar, so certain plants prey upon insects, literally eating them or absorbing them into their system. Best known among these are the pitcher plants, a swamp species, whose leaves are pitcher-like and with a hood or awning over the top to keep out the rain; these leaves are half filled with a sweet fluid that attracts insects, makes them tipsy and causes their death in the watery grave, the plant feeding largely upon the resulting broth. ”

“ The insects of this section must be considered essentially beneficial to man, notwithstanding the occasional sting of a bee or wasp, the boring of a carpenter bee, or the importunities of the omnipresent ant. Not only do they furnish us with honey and wax, but they play so important a part in the destruction of insects injurious to vegetation that they may be looked upon as God-appointed guards over the vegetal kingdom—carrying the pollen from plant to plant, and insuring the fertilization of diœcious species, and the cross-fertilization of others ”

“ More than that, some are absolutely sterile to their own pollen when it is applied to their stigmas artificially! With insect aid, however, a single plant has produced more than 1,000,700 seeds. No wonder, then, that as a family, they have adopted the most marvellous blandishments and mechanism in the whole floral kingdom to secure the visits of that special insect to which each is adapted, and, having secured him, to compel him unwittingly to do their bidding. ”

“ Of course the insect visitors - bees and flies chiefly - alight on the showy staminate blossoms first, and transfer pollen from them to the dull pistillate ones later, as it was intended they should, to prevent self-fertilization. How endless are the devices of the flowers to guard against this evil and to compel insects to cross-pollinate them! The most minute detail of the mechanism involved, which the microscope reveals, only increases our interest and wonder.
Any plant which elects to grow in shallow water must be amphibious ”

“ Don't let the soil get full of insect troubles; therefore, keep the soil open and aired and study it well.
"There are two general classes of insects known by the way they do their work. One kind gnaws at the plant really taking pieces of it into its system. This kind of insect has a mouth fitted to do this work. Grasshoppers and caterpillars are of this sort. The other kind sucks the juices from a plant. This, in some ways, is the worst sort. Plant lice belong here, as do mosquitoes, which prey on us. All the scale insects fasten themselves on plants, and suck out the life of the plants. ”

“ If by some such means the plants are kept insect-free till they outgrow the protection, they will usually escape serious damage from insects thereafter. It is well to plant trap or decoy hills of cucumbers, squashes, or melons in advance of the regular planting, on which the bugs may be harvested. ”

“ For they are perhaps the most useful of all insects in the great game of securing cross-fertilization, as we shall presently see. Many other kinds of adult insects eat pollen directly and so add to the number of insect visitors.
No one has ever been able to explain the beautiful coloring of flowers, except that it serves as an attraction for insects and small birds. Like the honey or nectar, it seems to play no real part in the home economy of the flower, to be of not the least use otherwise. ”

“ Lying in ambush for chance insects, as these sundews and pitcher plants do, may seem nearly the limit of what is to be expected of leaves. Merely to be always on the job, with a plentiful supply of insect digester, might seem to be all that could well be expected from what, after all, are only modified leaves. But nature’s devices are infinite, and there are still other ways to accomplish the apparently impossible. In a small section of the southeastern States there grows a plant that not only lies passively in wait for insects, but actually captures them. ”

“ They belong to various families, and are found in all parts of the globe. But how can the firmly rooted plant capture and grasp the light-winged insect; how can it retain the same sufficiently long to let the digestive juices act upon it? Naturally, in many cases, the sticky substance which is secreted by the leaves is the active agent, as, for instance, one may observe small animals adhering to the resinous stem of the "flytrap." But many plants are provided with special organs for this purpose, and they are able to catch the most nimble of insects with ease and dispatch. ”

“ Insects and diseases are frequently so closely united, or so dependent upon each other, that the naturalist often finds it difficult to determine to which the fruit grower should attribute his losses. Some species of insects attack only diseased or dead plants; others only the living and healthy. If a plant shows signs of failing, we are inclined to speak of it as being diseased, whether the failure is caused by a lack of some element in the soil, attacks of parasitic fungi, or noxious insects. ”

“ No wind-fertilized plant ever has a whorl of gay petals; and though the converse is not quite true, yet almost all insect-fertilized plants are noticeable for their brilliant tints of red, white, blue, or yellow. The structures in which these pigments reside have no function whatsoever, except that of attracting the insect eye. They are produced by the plant at an enormous physiological expense; and, if their object were not to secure the visits of insects, they would be just so much dead loss to the species. ”

“ One can see insects stuck on them and vainly struggling to be free, and the hairs undoubtedly prevent green-fly and other such pests from interfering with the honey of the flower. In some of these cases it has been shown that the body of the insect is actually used as food, but that is more obvious with two interesting plants which specially devote themselves to the capture of insect prey. One of these is very often kept in the Boer farmhouses near Tulbagh, in South Africa, simply to attract the flies, which are a perfect pest in those dry valleys. ”

“ Every insect has its proper plant, or tribe of plants, which it naturally requires for its nourishment, and on which it generally lays its eggs, and that on the most concealed parts of the plant; and the plant, and insect which attacks it, are always natives of the same climate, and therefore endure the same degrees of heat and cold; consequently, when plants are attacked by their natural tribe of insects, it is an exceedingly nice and curious operation to exterminate them without injuring the plants, or stopping them in their natural growth. ”

“ These beetles hide under the leaves that cluster in sheltered nooks about or between the large roots of forest trees, where they can be found on any mild winter day, and may be carried to the green-house or to the window plants that are infested with plant-lice. They will not only devour these pests, but will soon lay eggs that hatch and produce the larvæ which are so voracious as to clear the plants in a short-time. A little attention to the habits of these insects may spare us great losses from the plant-lice. ”

“ The insects which are best adapted to fertilize flowers cannot probably increase much beyond definite limits, because in doing so they would lead to a corresponding increase of insectivorous birds and other animals which would keep them down. The chief fertilizers—bees and butterflies—have enemies at every stage of their growth, from the egg to the perfect insect, and their numbers are, therefore, limited by causes quite independent of the supply of vegetable food. ”

“ What more complicated relation between plant and animal can be imagined than this of the fly and fly-bush? A plant in need of nitrogenous food possesses effective traps for insects, from which this food is got. The plant is in need, too, of the services of insects for the pollination of its flowers. How can this plant, a death trap to insects, secure their service in pollination? Its large showy flowers attract many insects, but they find no honey to reward them for their visit, and if they linger about the plant their doom is sealed. ”

“ Each insect has its own particular favorite food plant or plants, and in many cases the eggs of the insect are laid on the food plant so that the young may have food close at hand. Some insects prefer the rotted wood of trees. An American zoölogist, Packard, has estimated that over 450 kinds of insects live upon [Pg 34] oak trees alone. Everywhere animals are engaged in taking their nourishment from plants, and millions of dollars of damage is done every year to gardens, fruits, and cereal crops by insects. ”

“ The injuries occasioned by plant-lice, are much greater than would at first be expected, from an observation of the small size and extreme weakness of the insects; but these make up by their numbers what they lack in strength individually, and thus become formidable enemies to vegetation. By their punctures and the quantity of sap they draw from the leaves, the functions of these important organs are deranged, or interrupted, the sap is withdrawn or contaminated, and unfitted to supply the wants of vegetation. Plants are differently affected ”

“ The Venus’s-flytrap does not seem to depend alone on the chance lighting of the insect upon it. It has a sweet juice on the leaf to attract insects. But it does not need as much sticky fluid as the sun-dew, to hold the insect. The two halves of the leaf snap together like a trap. They give the insect no time to get away.
Another very odd plant which eats insects is the side-saddle plant. This is often called the pitcher-plant. [Pg 77] It looks far more like a pitcher than like a saddle. The leaves of this plant are like a beautiful pitcher painted red and green. ”

“ If plants have insect benefactors, they have their foes as well and hordes of tiny aphids, commonly known as green flies or plant lice, moored by their sucking tubes to the tender sprays of roses, wild and cultivated, live by extracting their juices. ”

“ While, as we have seen, thousands of plants rely upon insects for producing their young, still other thousands put everything to the hazard of the wind. Pollen is so light that it can easily be blown very great distances, and while the wastage is enormous, the process works so well that the greater part of the vegetation of the earth is thus fertilized. This is true not as to the number of different kinds of plants, for in that respect insect fertilization is more important than that accomplished by the wind. ”

“ It causes the leaves to turn yellow and checks new growth. Making right the harmful conditions will usually renew the health of the plant, but in bad cases it will be far better to remove the earth, wash the soil from the roots, carefully clean the pot—if the same one is to be used—and repot in good porous fresh earth. Keep on the dry side until growth is resumed.
As a rule, insects do much more damage to house plants than is caused by diseases. One characteristic of nearly all plant insects which will astonish the amateur is the marvelous rapidity with which they increase. ”

“ NECTAR OF PLANTS INTENDED TO ATTRACT INSECTS.
The secretion of saccharine matter in the nectaries of flowers is shown to be one of the normal functions of the plant, taking place at the season when it is desirable to attract the visits of insects for the purposes of its fertilisation. It may, then, be fairly asserted that the insect, when it carries off the honey from any blossom it has visited, is merely taking with it the fee or reward provided by nature for that special service. ”

“ Not only may such insects weaken the infested plants, but they also cause the destruction of chlorophyll, interfere with the normal functioning of the stomata, and have a toxic effect upon the tissues; further, many serious plant diseases are carried and spread by sucking insects, whilst the punctures made when feeding may allow the entry of disease spores. ”