The enormous injuries which insects cause to man may thus be held as one reason for ceasing to consider the study of them as an insignificant pursuit; for a knowledge of their structure, their food, their enemies, and their general habits, may lead, as it often has led, to the means of guarding against their injuries. At the same time we derive from them both direct and indirect benefits. The honey of the bee, the dye of the cochineal, and the web of the silk-worm, the advantages of which are obvious, may well be balanced against the destructive propensities of insects which are offensive to man. But a philosophical study of natural history will teach us that the direct benefits which insects confer upon us are even less important than their general uses in maintaining the economy of the world. The mischiefs which result to us from the rapid increase and the activity of insects are merely results of the very principle by which they confer upon us numberless indirect advantages. Forests are swept away by minute beetles; but the same agencies relieve us from that extreme abundance of vegetable matter which would render the earth uninhabitable were this excess not periodically destroyed. In hot countries the great business of removing corrupt animal matter, which the vulture and hyæna imperfectly perform, is effected with certainty and speed by the myriads of insects that spring from the eggs deposited in every carcase by some fly seeking therein the means of life for her progeny. Destruction and reproduction, the great laws of nature, are carried on very greatly through the instrumentality of insects; and the same principle regulates even the increase of particular species of insects themselves. When aphides are so abundant that we know not how to escape their ravages, flocks of lady-birds instantly cover our fields and gardens to destroy them. Such considerations as these are thrown out to show that the subject of insects has a great philosophical importance—and what portion of the works of nature has not? The habits of all God’s creatures, whether they are noxious, or harmless, or beneficial, are worthy objects of our study. If they affect ourselves, in our health or our possessions, whether for good or for evil, an additional impulse is naturally given to our desire to attain a knowledge of their properties. Such studies form one of the most interesting occupations which can engage a rational and inquisitive mind; and, perhaps, none of the employments of human life are more dignified than the investigation and survey of the workings and the ways of nature in the minutest of her productions.
The exercise of that habit of observation which can alone make a naturalist—“an out-of-door naturalist,” as Daines Barrington calls himself—is well calculated to strengthen even the most practical and merely useful powers of the mind. One of the most valuable mental acquirements is the power of discriminating among things which differ in many minute points, but whose general similarity of appearance usually deceives the common observer into a belief of their identity. The study of insects, in this point of view, is most peculiarly adapted for youth. According to our experience, it is exceedingly difficult for persons arrived at manhood to acquire this power of discrimination; but, in early life, a little care on the part of the parent or teacher will render it comparatively easy. In this study the knowledge of things should go along with that of words. “If names perish,” says Linnæus, “the knowledge of things perishes also:”[J] and, without names, how can any one communicate to another the knowledge he has acquired relative to any particular fact, either of physiology, habit, utility, or locality? On the other hand, mere catalogue learning is as much to be rejected as the loose generalizations of the despisers of classification and nomenclature. To name a plant, or an insect, or a bird, or a quadruped rightly, is one step towards an accurate knowledge of it; but it is not the knowledge itself. It is the means, and not the end in natural history, as in every other science.
If the bias of opening curiosity be properly directed, there is not any branch of natural history so fascinating to youth as the study of insects. It is, indeed, a common practice in many families to teach children, from their earliest infancy, to treat the greater number of insects as if they were venomous and dangerous, and, of course, meriting to be destroyed, or at least avoided with horror. Associations are by this means linked with the very appearance of insects, which become gradually more inveterate with advancing years; provided, as most frequently happens, the same system be persisted in, of avoiding or destroying almost every insect which is unlucky enough to attract observation. How much rational amusement and innocent pleasure is thus thoughtlessly lost; and how many disagreeable feelings are thus created, in the most absurd manner! In order to show that the study or (if the word be disliked) the observation of insects is peculiarly fascinating to children, even in their early infancy, we may refer to what we have seen in the family of a friend, who is partial to this, as well as to all the departments of natural history. Our friend’s children, a boy and girl, were taught, from the moment they could distinguish insects, to treat them as objects of interest and curiosity, and not to be afraid even of those which wore the most repulsive appearance. The little girl, for example, when just beginning to walk alone, encountered one day a large staphylinus (Goërius olens? Stephens; vulgo, the devil’s coach-horse), which she fearlessly seized, and did not quit her hold, though the insect grasped one of her fingers in his formidable jaws. The mother, who was by, knew enough of the insect to be rather alarmed for the consequences, though she prudently concealed her feelings from the child. She did well; for the insect was not strong enough to break the skin, and the child took no notice of its attempts to bite her finger. A whole series of disagreeable associations with this formidable-looking family of insects was thus averted at the very moment when a different mode of acting on the part of the mother would have produced the contrary effect. For more than two years after this occurrence the little girl and her brother assisted in adding numerous specimens to their father’s collection, without the parents ever having cause, from any accident, to repent of their employing themselves in this manner. The sequel of the little girl’s history strikingly illustrates the position for which we contend. The child happened to be sent to a relative in the country, where she was not long in having carefully instilled into her mind all the usual antipathies against “everything that creepeth on the earth;” and though she afterwards returned to her paternal home, no persuasion or remonstrance could ever again persuade her to touch a common beetle, much less a staphylinus, with its tail turned up in a threatening attitude, and its formidable jaws ready extended for attack or defence.[K] We do not wish that children should be encouraged to expose themselves to danger in their encounters with insects. They should be taught to avoid those few which are really noxious—to admire all—to injure none.
The various beauty of insects—their glittering colours, their graceful forms—supplies an inexhaustible source of attraction. Even the most formidable insects, both in appearance and reality,—the dragon-fly, which is perfectly harmless to man, and the wasp, whose sting every human being almost instinctively shuns,—are splendid in their appearance, and are painted with all the brilliancy of natural hues. It has been remarked that the plumage of tropical birds is not superior in vivid colouring to what may be observed in the greater number of butterflies and moths.[L] “See,” exclaims Linnæus, “the large, elegant painted wings of the butterfly, four in number, covered with delicate feathery scales! With these it sustains itself in the air a whole day, rivalling the flight of birds and the brilliancy of the peacock. Consider this insect through the wonderful progress of its life,—how different is the first period of its being from the second, and both from the parent insect! Its changes are an inexplicable enigma to us: we see a green caterpillar, furnished with sixteen feet, feeding upon the leaves of a plant; this is changed into a chrysalis, smooth, of golden lustre, hanging suspended to a fixed point, without feet, and subsisting without food; this insect again undergoes another transformation, acquires wings, and six feet, and becomes a gay butterfly, sporting in the air, and living by suction upon the honey of plants. What has nature produced more worthy of our admiration than such an animal, coming upon the stage of the world, and playing its part there under so many different masks?” The ancients were so struck with the transformations of the butterfly, and its revival from a seeming temporary death, as to have considered it an emblem of the soul, the Greek word pysche signifying both the soul and a butterfly; and it is for this reason that we find the butterfly introduced into their allegorical sculptures as an emblem of immortality. Trifling, therefore, and perhaps contemptible, as to the unthinking may seem the study of a butterfly, yet when we consider the art and mechanism displayed in so minute a structure,—the fluids circulating in vessels so small as almost to escape the sight—the beauty of the wings and covering—and the manner in which each part is adapted for its peculiar functions,—we cannot but be struck with wonder and admiration, and allow, with Paley, that “the production of beauty was as much in the Creator’s mind in painting a butterfly as in giving symmetry to the human form.”
A collection of insects is to the true naturalist what a collection of medals is to the accurate student of history. The mere collector, who looks only to the shining wings of the one, or the green rust of the other, derives little knowledge from his pursuit. But the cabinet of the naturalist becomes rich in the most interesting subjects of contemplation, when he regards it in the genuine spirit of scientific inquiry. What, for instance, can be so delightful as to examine the wonderful variety of structure in this portion of the creation; and, above all, to trace the beautiful gradations by which one species runs into another? Their differences are so minute, that an unpractised eye would proclaim their identity; and yet, when the species are separated, and not very distantly, they become visible even to the common observer. It is in examinations such as these that the naturalist finds a delight of the highest order. While it is thus one of the legitimate objects of his study to attend to minute differences of structure, form, and colouring, he is not less interested in the investigation of habits and economy; and in this respect the insect world is inexhaustibly rich. We find herein examples of instinct to parallel those of all the larger animals, whether they are solitary or social; and innumerable others besides, altogether unlike those manifested in the superior departments of animated nature. These instincts have various directions, and are developed in a more or less striking manner to our senses, according to the force of the motive by which they are governed. Some of their instincts have for their object the preservation of insects from external attack; some have reference to procuring food, and involve many remarkable stratagems; some direct their social economy, and regulate the condition under which they live together either in monarchies or republics, their colonizations, and their migrations; but the most powerful instinct which belongs to insects has regard to the preservation of their species. We find, accordingly, that as the necessity for this preservation is of the utmost importance in the economy of nature, so for this especial object many insects, whose offspring, whether in the egg or the larva state, are peculiarly exposed to danger, are endued with an almost miraculous foresight, and with an ingenuity, perseverance, and unconquerable industry, for the purpose of avoiding those dangers, which are not to be paralleled even by the most singular efforts of human contrivance. The same ingenuity which is employed for protecting either eggs, or caterpillars and grubs, or pupæ and chrysalides, is also exercised by many insects for their own preservation against the changes of temperature to which they are exposed, or against their natural enemies. Many species employ those contrivances during the period of their hibernation, or winter sleep. For all these purposes some dig holes in the earth, and form them into cells; others build nests of extraneous substances, such as bits of wood and leaves; others roll up leaves into cases, which they close with the most curious art; others build a house of mud, and line it with the cotton of trees, or the petals of the most delicate flowers; others construct cells, of secretions from their own bodies; others form cocoons, in which they undergo their transformation; and others dig subterraneous galleries, which, in their complexity of arrangement, in solidity, and in complete adaptation to their purposes, vie with the cities of civilised man. The contrivances by which insects effect these objects have been accurately observed and minutely described, by patient and philosophical inquirers, who knew that such employments of the instinct with which each species is endowed by its Creator offered the most valuable and instructive lessons, and opened to them a wide field of the most delightful study. The construction of their habitations is certainly among the most remarkable peculiarities in the economy of insects; and it is of this subject that we propose to treat under the general name, which is sufficiently applicable to our purpose, of Insect Architecture.
In the descriptions which we shall give of Insect Architecture, we shall employ as few technical words as possible: and such as we cannot well avoid, we shall explain in their places; but, since our subject chiefly relates to the reproduction of insects, it may be useful to many readers to introduce here a brief description of the changes which they undergo.
Magnified eggs, of a, Geometra armillata; b, of an unknown water insect; c, of the lacquey moth; d, of a caddis-fly (Phryganea atrata); e, of red under-wing moth (Catocala nupta); f, of Pontia Brassicæ; g, of the Clifden Nonpareil moth.
It was of old believed that insects were produced spontaneously by putrefying substances; and Virgil gives the details of a process for creating a swarm of bees out of the carcase of a bull; but Redi, a celebrated Italian naturalist, proved by rigid experiments that they are always, in such cases, hatched from eggs previously laid. Most insects, indeed, lay eggs, though some few are viviparous, and some propagate both ways. The eggs of insects are very various in form, and seldom shaped like those of birds. We have here figured those of several species, as they appear under the microscope.
When an insect first issues from the egg, it is called by naturalists larva, and, popularly, a caterpillar, a grub, or a maggot. The distinction, in popular language, seems to be, that caterpillars are produced from the eggs of moths or butterflies; grubs from the eggs of beetles, bees, wasps, &c.; and maggots (which are without feet) from blow-flies, house-flies, cheese-flies, &c., though this is not very rigidly adhered to in common parlance. Maggots are also sometimes called worms, as in the instance of the meal-worm; but the common earth-worm is not a larva, nor is it by modern naturalists ranked among insects.