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OUR COMMON INSECTS.
OUR
COMMON INSECTS.
A POPULAR ACCOUNT OF THE INSECTS
OF OUR
Fields, Forests, Gardens and Houses.
Illustrated with 4 Plates and 268 Woodcuts.
BY
A. S. PACKARD, JR.,
Author of "A GUIDE TO THE STUDY OF INSECTS."
SALEM. NATURALISTS' AGENCY. BOSTON: Estes & Lauriat. NEW YORK: Dodd & Mead. 1873.
Entered, according to Act of Congress, in the year 1878, by F. W. PUTNAM & CO., in the Office of the Librarian of Congress at Washington.
PRINTED AT THE SALEM PRESS, F. W. PUTNAM & CO., Proprietors.
DEDICATION.
TO SAMUEL H. SCUDDER.
MY DEAR SCUDDER:—You and I were drawn together many years ago by a common love for insects and their ways.
I dedicate this little volume of ephemeral essays to you in recognition of your worth as a man and a scientist, and as a token of warm friendship.
Yours sincerely,
A. S. PACKARD, JR.
PREFACE.
This little volume mainly consists of a reprint of a series of essays which appeared in the "American Naturalist" (Vols. i-v, 1867-71). It is hoped that their perusal may lead to a better acquaintance with the habits and forms of our more common insects. The introduction was written expressly for this book, as well as Chapter XIII, "Hints on the Ancestry of Insects." The scientific reader may be drawn with greater interest to this chapter than to any other portion of the book. In this discussion of a perhaps abstruse and difficult theme, his indulgence is sought for whatever imperfections or deficiencies may appear. Our systems of classification may at least be tested by the application of the theory of evolution. The natural system, if we mistake not, is the genealogy of organized forms; when we can trace the latter, we establish the former. Considering how much naturalists differ in their views as to what is a natural classification, it is not strange that a genealogy of animals or plants seems absurd to many. To another generation of naturalists it must, perhaps, be left to decide whether to attempt the one is more unphilosophical than to attempt the other.
Most of the cuts have already appeared in the "Guide to the Study of Insects" and the "American Naturalist," where their original sources are given, while a few have been kindly contributed by Prof. A. E. Verrill, the Boston Society of Natural History, and Prof. C. V. Riley, and three are original.
SALEM, June, 1873.
OUR COMMON INSECTS.
INTRODUCTORY.
What is an Insect? When we remember that the insects alone comprise four-fifths of the animal kingdom, and that there are upwards of 200,000 living species, it would seem a hopeless task to define what an insect is. But a common plan pervades the structure of them all. The bodies of all insects consist of a succession of rings, or segments, more or less hardened by the deposition of a chemical substance called chitine; these rings are arranged in three groups: the head, the thorax, or middle body, and the abdomen or hind body. In the six-footed insects, such as the bee, moth, beetle or dragon fly, four of these rings unite early in embryonic life to form the head; the thorax consists of three, as may be readily seen on slight examination, and the abdomen is composed either of ten or eleven rings. The body, then, seems divided or insected into three regions, whence the name insect.
The head is furnished with a pair of antennae, a pair of jaws (mandibles), and two pairs of maxillae, the second and basal pair being united at their base to form the so-called labium, or under lip. These four pairs of appendages represent the four rings of the head, to which they are appended in the order stated above.
A pair of legs is appended to each of the three rings of the thorax; while the first and second rings each usually carry a pair of wings.
The abdomen contains the ovipositor; sometimes, as in the bees and wasps, forming a sting. In the spiders (Fig. 1), however, there are no antennae, and the second maxillae, or labium, is wanting. Moreover, there are four pairs of legs. The centipedes (Fig. 2, a Myriopod) also differ from the rest of the insects in having an indefinite number of abdominal rings, each bearing a pair of legs.
On examining the arrangement of the parts within, we find the nervous cord, consisting of two chains of swellings, or nerve-knots, resting upon the floor or under side of the body; and the heart, or dorsal vessel, situated just under the skin of the back; and in looking at living caterpillars, such as the cut-worm, and many thin-skinned aquatic larvae, we can see this long tubular heart pulsating about as often as our own heart, and when the insect is held against its will, or is agitated, the rapidity of the pulsations increases just as with us.
Insects do not breathe as in the higher animals by taking the air into the mouth and filling the lungs, but there are a series of holes or pores along the side of the body, as seen in the grub of the humble bee, through which the air enters and is conveyed to every part of the body by an immense number of air tubes. (Fig. 3, air tubes, or tracheae, in the caudal appendage of the larva of a dragon fly). These air tubes are everywhere bathed by the blood, by which the latter becomes oxygenated.
Indeed the structure of an insect is entirely different from that of man or the quadrupeds, or any other vertebrate animal, and what we call head, thorax, abdomen, gills, stomach, skin, or lungs, or jaws, are called so simply for convenience, and not that they are made in the same way as those parts in the higher animals.
An insect differs from a horse, for example, as much as a modern printing press differs from the press Franklin used. Both machines are made of iron, steel, wood, etc., and both print; but the plan of their structure differs throughout, and some parts are wanting in the simpler press which are present and absolutely essential in the other. So with the two sorts of animals; they are built up originally out of protoplasm, or the original jelly-like germinal matter, which fills the cells composing their tissues, and nearly the same chemical elements occur in both, but the mode in which these are combined, the arrangement of their products: the muscular, nervous and skin tissues, differ in the two animals. The plan of structure, namely, the form and arrangement of the body walls, the situation of the appendages to the body, and of the anatomical systems within, i.e., the nervous, digestive, circulatory, and respiratory systems, differ in their position in relation to the walls of the body. Thus while the two sorts of animals reproduce their kind, eat, drink and sleep, see, hear and smell, they perform these acts by different kinds of organs, situated sometimes on the most opposite parts of the body, so that there is no comparison save in the results which they accomplish; they only agree in being animals, and in having a common animal nature.
How Insects Eat. The jaws of insects (Fig. 4) are horny processes situated on each side of the mouth. They are variously toothed, so as to tear the food, and move horizontally instead of up and down as in the horse. The act of taking the food, especially if the insect be carnivorous in its habits, is quite complex, as not only the true jaws, but the accessory jaws (maxillae, Fig. 5, a, upper, b, under side of the head of a young beetle; at, antennae, md, mandible, mx, maxillae, mx[1], labium) and the feelers (palpi) attached to the maxillae, and the under lip (labium) are of great service in enabling the insect to detect its food both by the senses of touch and smell. The maxillae are in the fully grown beetle (Fig. 6) divided into three lobes, the outermost forming the palpus, and the two others forming sharp teeth, often provided with hairs and minute brushes for cleansing the adjoining parts; these strong curved teeth are used in seizing the food and placing it between the grinders, where it is crushed, prepared for digestion and swallowed. Fig. 7 represents the mouth parts of the humble bee. (b, upper lip; d, mandible; e, maxilla; f, maxillary palpus; g, tongue; ih, labium and tabial palpi; k, eye.)
The alimentary canal passes through the middle of the body, the stomach forming usually a simple enlargement. Just before the stomach in certain insects, as the grasshopper, is a gizzard armed with rows of powerful horny teeth for finely crushing grass.
Insects eat almost incredible quantities of food when young and growing rapidly. Mr. Trouvelot tells us in the "American Naturalist" that the food taken by a single American Silk-worm in fifty-six days is equal to eighty-six thousand times its primitive weight! On the other hand, after the insect has finished its transformations, it either takes no food at all, as in the May fly, or merely sips the honey of flowers, as in the butterfly, while the June beetle and many others like it eat the leaves of trees, and the tiger and ground beetles feed voraciously on other insects.
How Insects Walk. In man and his allies, the vertebrates, the process of walking is a most difficult and apparently dangerous feat. To describe the mechanics of walking, the wonderful adaptation of the muscles and bones for the performance of this most ordinary action of life, would require a volume. The process is scarcely less complex in insects. Lyonnet found 3,993 muscles in a caterpillar, and while a large proportion belong to the internal organs, over a thousand assist in locomotion. Hence the muscular power of insects is enormous. A flea will leap two hundred times its own height, and certain large, solid beetles will move enormous weights as compared to the bulk of their bodies.
In walking, as seen in the accompanying figure (Fig. 8), three legs are thrown forward at a time, two on one side and one on the other.
Flies and many other insects can walk upside down, or on glass, as easily as on a level surface. A fly's foot, as in most other insects, consists of five joints (tarsal joints), to the last one of which is appended a pair of stout claws, beneath which is a flat, soft, fleshy cushion or pad, split into two (sometimes three) flaps, beset on the under surface with fine hairs. A part of these hairs are swollen at the end, which is covered with "an elastic membranous expansion, capable of close contact with a highly polished surface, from which a minute quantity of a clear, transparent fluid is emitted when the fly is actively moving." (T. West.) These hairs are hence called holding, or tenent, hairs. With the aid of these, but mainly, as Mr. West insists, by the pressure of the atmosphere, a fly is enabled to adhere to perfectly smooth surfaces. His studies show the following curious facts. "That atmospheric pressure, if the area of the flaps be alone considered, is equal to just one-half the weight of a fly. If the area covered by the tenent hairs be added, an increase of pressure is gained, equal to about one-fourth the weight of a fly. This leaves one-fourth to be accounted for by slight viscidity of the fluid, by the action I have so often alluded to, which may be called 'grasping,' by molecular attraction, and, doubtless, by other agents still more subtle, with which we have at present scarcely any acquaintance."
How Insects Fly. Who of us, as remarked by an eminent ornithologist, can even now explain the long sustained, peculiar flight of the hawk, or turkey buzzard, as it sails in the air without changing the position of its wings? and, we would add, the somewhat similar flight of a butterfly? It is the poetry of motion, and a marvellous exhibition of grace and ease, combined with a wonderful underlying strength and lightness of the parts concerned in flight.
Before we give a partial account of the results obtained by the delicate experiments of Professor Marey on the flight of birds and insects, our readers should be reminded of the great differences between an insect and a bird, remembering that the former, is, in brief, a chitinous sac, so to speak, or rather a series of three such spherical or elliptical sacs (the head, thorax and abdomen); the outer walls of the body forming a solid but light crust, to which are attached broad, membranous wings, the wing being a sort of membranous bag stretched over a framework of hollow tubes (the tracheae), so disposed as to give the greatest lightness and strength to the wing. The wings are moved by powerful muscles of flight, filling up the cavity of the thorax, just as the muscles are the largest about the thorax of a bird. Moreover in the bodies of insects that fly (such as the bee, cockchafer, and dragon fly), as distinguished from those that creep exclusively, the air tubes (tracheae) which ramify into every part of the body, are dilated here and there, especially in the base of the abdomen, into large sacs, which are filled with air when the insect is about to take flight, so that the specific gravity of the body is greatly diminished. Indeed, these air sacs, dilatable at will by the insect, may be compared to the swimming bladder of fishes, which enables them to rise and fall at will to different levels in the sea, thus effecting an immense saving of the labor of swimming. In the birds, as every body knows who has eaten a chicken, or attended the dissection of a Thanksgiving turkey, the soft parts are external, attached to the bony framework comprising the skeleton, the wing bones being directly connected with the central back bone; so that while these two sorts of animated flying machines are so different in structure, they yet act in much the same manner when on the wing. The difference between them is clearly stated by Marey, some of whose conclusions we now give almost word for word.
The flight of butterflies and moths differs from that of birds in the almost vertical direction of the stroke of their wings, and in their faculty of sailing in the air without making any movements; though sometimes in the course they pursue they seem to resemble birds in their flight.
The flight of insects and birds moreover differs in the form of the trajectory in space; in the inclination of the plane in which the wings beat; in the role of each of the two alternating (and in an inverse sense) movements that the wings execute; as also in the facility with which the air is decomposed during these different movements. As the wings of a fly are adorned with a brilliant array of colors, we can follow the trajectory or figure that each wing writes in the air. It is of the form of a figure of eight (Fig. 9), first discovered by Professor J. Bell Pettigrew of Edinburgh.
By an ingenious machine, specially devised for the purpose, Professor Marey found that a bird's wing moves in an ellipse, with a pointed summit (Fig. 10). The insect beats the air in a distinctly horizontal plane, but the bird in a vertical plane. The wing of an insect is impervious to the air; while the bird's wing resists the air only on its under side. Hence, there are two sorts of effects; in the insect the up and down strokes are active; in the bird, the lowering of the wing is the only active period, though the return stroke seems to sustain the bird, the air acting on the wing. The bird's body is horizontal when the wing gives a downward stroke; but when the beat is upward, the bird is placed in an inclined plane like a winged projectile, and mounts up on the air by means of the inclined surfaces that it passively offers to the resistance of this fluid.
In an insect, an energetic movement is equally necessary to strike the air at both beats up and down. In the bird, on the contrary, one active beat only is necessary, the down beat. It creates at that time all the motive force that will be dispensed during the entire revolution of the wing. This difference is due to the difference in form of the wing. The difference between the two forms of flight is shown by an inspection of the two accompanying figures (11, 12). An insect's wing is small at the base and broad at the end. This breadth would be useless near the body, because at this point the wing does not move swiftly enough to strike the air effectively. The type of the insectean wing is designed, then, simply to strike the air. But in the bird the wing plays also a passive role, i. e., it receives the pressure of the air on its under side when the bird is projected rapidly onward by its acquired swiftness. In these conditions the whole animal is carried onward in space; all the points of its wing have the same velocity. The neighboring regions of the body are useful to press upon the air, which acts as on a paper kite. The base of the wing also, in the bird, is broad, and provided with feathers, which form a broad surface, on which the air presses with a force and method very efficacious in supporting the bird. Fig. 12 gives an idea of this disposition of the wing at the active and passive time in a bird.
The inner half of the wing is the passive part of the organ, while the external half, that which strikes the air, is the active part. A fly's wing makes 330 revolutions in a second, executing consequently 660 simple oscillations; it ought at each time to impress a lateral deviation of the body of the insect, and destroy the velocity that the preceding oscillation has given it in a contrary direction. So that by this hypothesis the insect in its flight only utilizes fifty to one hundred parts (or one-half) of the resistance that the air furnishes it.
In the bird (Fig. 13), at the time of lowering the wings, the oblique plane which strikes the air, in decomposing the resistance, produces a vertical component which resists the weight of the body, and a horizontal component which imparts swiftness. The horizontal component is not lost, but is utilized during the rise of the wing, as in a paper kite when held in the air against the wind. Thus the bird utilizes seventy-five out of one hundred parts of the resistance that the air furnishes. The style of flight of birds is, therefore, theoretically superior to that of insects. As to the division of the muscular force between the resistance of the air and the mass of the body of the bird, we should compare the exertion made in walking on sand, for example, as compared with walking on marble. This is easy to measure. When a fish strikes the water with its tail to propel itself forward, it performs a double task; one part consists in pushing backwards a certain mass of water with a certain swiftness, and the other in pushing on the body in spite of the resistance of the surrounding fluid. This last portion of the task only is utilized. It would be greater if the tail of the fish encountered a solid object. Almost all the propelling agencies employed in navigation undergo this loss of labor, which depends on the mobility of the point d' appui. The bird is placed among conditions especially unfavorable.
The Senses of Insects. The eyes of insects are sometimes so large as to envelop the head like an Elizabethan ruffle, and the creature's head, as in the common house fly, seems all eyes. And this is almost literally the case, as the two great staring eyes that almost meet on the top of the head to form one, are made up of myriads of simple eyes. Each facet or simple eye is provided with a nerve filament which branches off from the main optic nerve, so that but one impression of the object perceived is conveyed to the brain; though it is taught by some that objects appear not only double but a thousand times multiplied. But we should remember that with our two eyes we see double only when the brain is diseased. Besides the large ordinary compound eyes, many insects possess small, simple eyes, like those of the spider. The great German anatomist, Johannes Mueller, believed that the compound eyes were adapted for the perception of distant objects, while those nearer are seen by the simple eyes. But it may be objected to this view that the spiders, which have only simple eyes, apparently see both near and remote objects as well as insects.
The sense of touch is diffused all over the body. As in the hairs of the head and face of man, those of insects are delicate tactile organs; and on the antennae and legs (insects depending on this sense rather than that of sight) these appendages are covered with exquisitely fine hairs. It is thought by some that the senses of hearing and smell are lodged in the antennae, these organs thus combining the sense of feeling with those of hearing and smelling. And the researches of anatomists lend much probability to the assertion, since little pits just under the skin are found, and even sometimes provided with grains of sand in the so-called ear of the lobster, etc., corresponding to the ear bones of the higher animals, the pits being connected with nerves leading to the brain. We have detected similar pits in the under side of the palpi of the Perla. It seems not improbable that these are organs of smell, and placed in that part of the appendage nearest the mouth, so as to enable the insect to select its proper food by its odor. Similar organs exist on the caudal appendages of a kind of fly (Chrysopila), while the long, many-jointed caudal filaments of the cockroach are each provided with nearly a hundred of these little pits, which seem to be so many noses. Thus Lespes, a Swiss anatomist, in his remarks on the auditory sacs, which he says are found in the antennae of nearly all insects, declares that as we have in insects compound eyes, so we have compound ears. We might add that in the abdominal appendage of the cockroach we have a compound nose, while in the feelers of the Perla, and the caudal appendage of the Chrysopila, the "nose" is simple. We might also refer here to Siebold's discovery of ears at the base of the abdomen of some, and in the forelegs of other kinds, of grasshoppers. Thus we need not be surprised at finding ears and noses scattered, as it were, sometimes almost wantonly over the bodies of insects (in many worms the eyes are found all over the body), while in man and his allies, from the monkey down to the fish, the ears and nose invariably retain the same relative place in the head.
How Insects Grow. When beginning our entomological studies no fact seemed more astonishing to our boyish mind than the thought that the little flies and midges were not the sons and daughters of the big ones. If every farmer and gardener knew this single fact it would be worth their while. The words larva and pupa will frequently occur in subsequent pages, and they should be explained. The caterpillar (Fig. 14, a) represents the earliest stage or babyhood of the butterfly, and it is called larva, from the Latin, meaning a mask, because it was thought by the ancients to mask the form of the adult butterfly.
When the caterpillar has ended its riotous life, for its appetite almost transforms its being into the very incarnation of gluttony, it suddenly, as if repenting of its former life as a bon vivant, seeks a solitary cell or hole where like a hermit it sits and leads apparently about as useless an existence. But meanwhile strange processes are going on beneath the skin; and after a few convulsive struggles the back splits open, and out wriggles the chrysalis, a gorgeous, mummy-like form, its body adorned with golden and silvery spots. Hence the word chrysalis (Fig. 14, b), from the Greek, meaning golden, while the Latin word pupa, meaning a baby or doll, is indicative of its youth. In this state it hangs suspended to a twig or other object; while the silk worm, and others of its kind, previous to moulting, or casting their skins, spin a silken cocoon, which envelops and protects the chrysalis.
At the given time, and after the body of the adult has fully formed beneath the chrysalis skin, there is another moult, and the butterfly, with baggy, wet wings, creeps out. The body dries, the skin hardens, the wings expand, and in a few moments, sometimes an hour, the butterfly (Fig. 15) proudly sails aloft, the glory and pride of the insect world.
We shall see in the ensuing chapters how varied are the larvae and pupae of insects, and under what different guises insects live in their early stages.
OUR COMMON INSECTS.
CHAPTER I.
THE HOME OF THE BEES.
The history of the Honey bee, its wonderful instincts, its elaborate cells and complex economy, have engrossed the attention of the best observers, even from the time of Virgil, who sang of the Ligurian bee. The literature of the art of bee-keeping is already very extensive. Numerous bee journals and manuals of bee-keeping testify to the importance of this art, while able mathematicians have studied the mode of formation of the hexagonal cells,[1] and physiologists have investigated the intricate problems of the mode of generation and development of the bee itself.
In discussing these difficult questions, we must rise from the study of the simple to the complex, remembering that—
"All nature widens upward. Evermore The simpler essence lower lies: More complex is more perfect—owning more Discourse, more widely wise."
and not forget to study the humbler allies of the Honey bee. We shall, in observing the habits and homes of the wild bees, gain a clearer insight into the mysteries of the hive.
The great family of bees is divided into social and solitary species. The social kinds live in nests composed of numerous cells in which the young brood are reared. These cells vary in form from those which are quite regularly hexagonal, like those of the Hive bee, to those which are less regularly six-sided, as in the stingless bee of the tropics (Melipona), until in the Humble bee the cells are isolated and cylindrical in form.
Before speaking of the wild bees, let us briefly review the life of the Honey bee. The queen bee having wintered over with many workers, lays her eggs in the spring, first in the worker, and, at a later period, in the drone-cells. Early in the summer the workers construct the large, flask-shaped queen-cells, which are placed on the edge of the comb, and in these the queen larvae are fed with rich and choice food. The old queen deserts the nest, forming a new colony. The new-born queen takes her marriage flight high in the air with a drone, and on her return undertakes the management of the hive, and the duty of laying eggs. When the supply of queens is exhausted, the workers destroy the drones. The first brood of workers live about six weeks in summer, and then give way to a new brood. The queens, according to Von Berlepsch, are known to live five years, and during their whole life lay more than a million eggs.
In the tropics, the Honey bee is replaced by the Meliponas and Trigonas. They are minute, stingless bees, which store up honey and live in colonies often of immense extent. The cells of Melipona are hexagonal, nearly approaching in regularity those of the Hive bee, while the honey cells are irregular, being much larger cavities, which hold about one-half as much honey as a cell of the Humble bee. "Gardner, in his travels, states that many species of Melipona build in the hollow trunks of trees, others in banks; some suspend their nests from the branches of trees, whilst one species constructs its nest of clay, it being of large size." (F. Smith.)
In a nest of the coal-black Trigona (Trigona carbonaria), from eastern Australia, Mr. F. Smith, of the British Museum, found from four hundred to five hundred dead workers, but no females. The combs were arranged precisely similar to those of the common wasp. The number of honey-pots which were placed at the foot of the nest was two hundred and fifty. Mr. Smith inclines to the opinion that the hive of Trigona contains several prolific females, as the great number of workers can only be thus explained, and M. Guerin found six females in a nest of the Tawny-footed Melipona (M. fulvipes).
At home, our nearest ally of the true Honey bee, is the Humble bee (Bombus), of which over forty species are known to inhabit North America.
The economy of the Humble bee is thus: the queen awakens in early spring from her winter's sleep under leaves or moss, or in the last year's nest, and selects a nesting place, generally in an abandoned nest of a field-mouse, or beneath a stump or sod, and "immediately," according to Mr. F. W. Putnam,[2] "collects" a small amount of pollen mixed with honey, and in this deposits from seven to fourteen eggs, gradually adding to the pollen mass until the first brood is hatched. She does not wait, however, for one brood to be hatched before laying the eggs of another, but, as soon as food enough has been collected, she lays the eggs for a second. The eggs are laid, in contact with each other, in one cavity of the mass of pollen, with a part of which they are slightly covered. They are very soon developed; in fact, the lines are nowhere distinctly drawn between the egg and the larva, the larva and pupa, and again between the latter and the imago; a perfect series, showing this gradual transformation of the young to the imago can be found in almost every nest.
"As soon as the larvae are capable of motion and commence feeding, they eat the pollen by which they are surrounded, and, gradually separating, push their way in various directions. Eating as they move, and increasing in size quite rapidly, they soon make large cavities in the pollen mass. When they have attained their full size, they spin a silken wall about them, which is strengthened by the old bees covering it with a thin layer of wax, which soon becomes hard and tough, thus forming a cell (Fig. 15, 1, cell containing a larva, on top of which (2) is a pollen mass containing three eggs). The larvae now gradually attain the pupa stage, and remain inactive until their full development. They then cut their way out, and are ready to assume their duties as workers, small females, males or queens.
"It is apparent that the irregular disposition of the cells is due to their being constructed so peculiarly by the larvae. After the first brood, composed of workers, has come forth, the queen bee devotes her time principally to her duties at home, the workers supplying the colony with honey and pollen. As the queen continues prolific, more workers are added, and the nest is rapidly enlarged.
"About the middle of summer, eggs are deposited, which produce both small females and males." ... "All eggs laid after the last of July produce the large females, or queens, and, the males being still in the nest, it is presumed that the queens are impregnated at this time, as on the approach of cold weather all except the queens, of which there are several in each nest, die."
While the Humble bee in some respects shows much less instinct than the solitary bees mentioned below, it stands higher in the series, however, from having workers, as well as males and females, who provide food for the young. The labors of the Mason bees, and their allies, terminate after the cell is once constructed and filled with pollen. The eggs are then left to hatch, and the young care for themselves, though the adult bee shows greater skill in architecture than the Humble bee. It is thus throughout nature. Many forms, comparatively low in the scale of life, astonish us with certain characters or traits, reminding us of beings much superior, physically and intellectually. The lower forms constantly reach up and in some way ally themselves with creatures far more highly organized. Thus the fish-like seal reminds us strikingly of the dog, both in the form of the head, in its docility and great intelligence when tamed, and even in its bark and the movements of the head.
The parasites of the Humble bee are numerous. Such are the species of Apathus, which so closely resembles the Humble bee itself, that it requires long study to distinguish it readily. Its habits are not known, other than that it is found in the nests of its host. It differs from the Humble bee in having no pollen-basket, showing that its larvae must feed on the food stored up by their host, as it does not itself collect it. The mandibles also are not, like those of Bombus, trowel-shaped for architectural purposes, but acutely triangular, and are probably not used in building.
The caterpillars of various moths consume the honey and waxen cells; the two-winged flies, Volucella and Conops, and the larvae of what is either an Anthomyia or Tachina-like fly, and several species of another genus of flies, Anthrax, together with several beetles, such as the Meloe (Fig. 16), Stylops (Fig. 17, male; 18b, female; a, position in the body of its host), and Antherophagus prey upon them.
The power of boring the most symmetrical tunnels in solid wood reaches its perfection in the large Virginian Carpenter bee (Xylocopa Virginica, Fig. 19). This bee is as large as, and some allied exotic species are often considerably larger than, the Humble bee, but not clothed with such dense hairs. We have received from Mr. James Angus, of West Farms, N. Y., a piece of trellis from a grape vine, made of pine wood, containing the cells and young in various stages of growth, together with the larvae and chrysalids of Anthrax sinuosa (Fig. 20), a species of fly parasitic on the larva. The maggot buries its head in the soft body of the young bee and feeds on its juices.
Mr. Angus thus writes us regarding its habits, under date of July 19: "I asked an intelligent and observing carpenter yesterday, if he knew how long it took the Xylocopa to bore her tunnel. He said he thought she bored about one-quarter of an inch a day. I don't think myself she bores more than one-half inch, if she does that. If I mistake not, it takes her about two days to make her own length at the first start; but this being across the grain of the wood, may not be so easily done as the remainder, which runs parallel with it. She always follows the grain of the wood, with the exception of the entrance, which is about her own length. The tunnels run from one to one and a half feet in length. They generally run in opposite directions from the opening, and sometimes other galleries are run, one directly above the other, using the same opening. I think they only make new tunnels when old ones are not to be found, and that the same tunnels are used for many years. Some of the old tunnels are very wide. I have found parts of them about an inch in diameter. I think this is caused by rasping off the sides to procure the necessary material for constructing their cells. The partitions are composed of wood raspings, and some sticky fluid, probably saliva, to make them adhere.
"The tunnels are sometimes taken possession of by other bees and wasps. I think when this is the case, the Xylocopa prefers making a new cell, to cleaning out the dirt and rubbish of the other species. I frequently find these bees remaining for a long time on the wing close to the opening, and bobbing their heads against the side, as if fanning air into the opening. I have seen them thus employed for twenty minutes. Whether one bee or more makes the tunnel, that is, whether they take turns in boring, I cannot at present say. In opening the cells (Fig. 21), more than one are generally found, even at this season. About two weeks ago; I found as many as seven, I think, in one."[3]
The hole is divided by partitions into cells about seven-tenths of an inch long. These partitions are constructed of the coarse dust or chippings made by the bee in eating out her cells, for our active little carpenter is provided with strong cutting jaws, moved by powerful muscles, and on her legs are stiff brushes of hair for cleaning out the tunnel as she descends into the heart of the solid wood. She must throw out the chips she bites off with her powerful mandibles from the sides of the burrow, by means of her hind legs, passing the load of chips backwards out of the cell with her fore limbs, which she uses as hands.
The partitions are built most elaborately of a single flattened band of chips, which is rolled up into a coil four layers deep. One side, forming the bottom of the cell, is concave, being beaten down and smoothed off by the bee. The other side of the partition, forming the top of the cell, is flat and rough.
At the time of opening the burrow, July 8th, the cells contained nearly full-grown larvae, with some half developed. They were feeding on the masses of pollen, which were as large as a thick kidney bean, and occupied nearly half the cell. The larvae (Fig. 21) resemble those of the Humble bee, but are slenderer, tapering more rapidly towards each end of the body.
The habits and structure of the little green Ceratina ally it closely with Xylocopa. This pretty bee, named Ceratina dupla by Mr. Say, tunnels out the stems of the elder or blackberry, syringa, or any pithy shrub, excavating them often to a depth of six or seven inches. She makes the walls just wide enough to admit her body, and of a depth capable of holding three or four, often five or six cells (Fig. 22). The finely built cells, with their delicate silken walls, are cylindrical and nearly square at each end, though the free end of the last cell is rounded off. They are four and a half tenths of an inch long, and a little over one-third as broad. The bee places them at nearly equal distances apart, the slight interval between them being filled in with dirt.
Dr. T. W. Harris states that May 15, 1832, one female laid its eggs in the hollow of an aster stalk. Three perfect insects were disclosed from it July 28th. The observations of Mr. Angus, who saw some bees making their cells May 18th, also confirm this account. The history of our little upholsterer is thus cleared up. Late in the spring she builds her cells, fills them with pollen, and lays one or more eggs upon each mass. Thus in about two months the insect completes its transformations; within this period passing through the egg, the larva and chrysalid states, and then, as a bee, living a few days more, if a male; or if a female, living through the winter. Her life thus spans one year.
The larva (Fig. 23) is longer than that of Megachile, and compared with that of Xylocopa, the different segments are much more convex, giving a serrate outline to the back of the worm. The pupa, or chrysalis, we have found in the cells the last of July. It is white, and three-tenths of an inch long. It differs from that of the Leaf-cutter bee in having four spines on the end of the body.
In none of the wild bees are the cells constructed with more nicety than those of our little Ceratina. She bores out with her jaws a long deep well just the size of her body, and then stretches a thin, delicate cloth of silk drawn tight as a drum-head across each end of her chambers, which she then fills with a mixture of pollen and honey.
Her young are not, in this supposed retreat, entirely free from danger. The most invidious foes enter and attack the brood. Three species of Ichneumon flies, two of which belong to the Chalcid family, lay their eggs within the body of the larva, and emerge from the dried larva and pupa skins of the bee, often in great numbers. The smallest parasite, belonging to the genus Anthophorabia, so called from being first known as a parasite on another bee (Anthophora), is a minute species found also abundantly in the tight cells of the Leaf-cutter bee.
The interesting habits of the Leaf-cutting, or Tailor bee (Megachile), have always attracted attention. This bee is a stout, thick-bodied insect, with a large, square head, stout, sharp, scissors-like jaws, and with a thick mass of stout, dense hairs on the under side of the tail for carrying pollen, as she is not provided with the pollen-basket of the Honey and Humble bees.
The Megachile lays its eggs in burrows in the stems of the elder (Fig. 24), which we have received from Mr. James Angus; we have also found them in the hollows of the locust tree. Mr. F. W. Putnam thus speaks of the economy of M. centuncularis, our most common species. "My attention was first called, on the 26th of June, to a female busily engaged in bringing pieces of leaf to her cells, which she was building under a board, on the roof of the piazza, directly under my window. Nearly the whole morning was occupied by the bee in bringing pieces of leaf from a rose bush growing about ten yards from her cells, returning at intervals of a half minute to a minute with the pieces, which she carried in such a manner as not to impede her steps when she alighted near her hole." When the Leaf-cutter bee wishes to cut out a piece of a leaf (Fig. 25) she alights upon the leaf, and in a few seconds swiftly runs her scissors-like jaws around through it, bearing off the piece in her hind legs. "About noon she had probably completed the cell, upon which she had been engaged, as, during the afternoon, she was occupied in bringing pollen, preparatory to laying her single egg in the cell. For about twenty days the bee continued at work, building new cells and supplying them with pollen.... On the 28th of July, upon removing the board, it was found that the bee had made thirty cells, arranged in nine rows of unequal length, some being slightly curved to adapt them to the space under the board. The longest row contained six cells, and was two and, three-quarters inches in length; the whole leaf structure being equal to a length of fifteen inches. Upon making an estimate of the pieces of leaf in this structure, it was ascertained that there must have been at least a thousand pieces used. In addition to the labor of making the cells, this bee, unassisted in all her duties, had to collect the requisite amount of pollen (and honey?) for each cell, and lay her eggs therein, when completed. Upon carefully cutting out a portion of one of the cells, a full-grown larva was seen engaged in spinning a slight silken cocoon about the walls of its prison, which were quite hard and smooth on the inside, probably owing to the movements of the larva, and the consequent pressing of the sticky particles to the walls. In a short time the opening made was closed over by a very thin silken web. The cells, measured on the inside of the hard walls, were .35 of an inch in length, and .15 in diameter. The natural attitude of the larva is somewhat curved in its cell, but if straightened, it just equals the inside length of the cell. On the 31st of July, two female bees came out, having cut their way through the sides of their cells." In three other cells "several hundred minute Ichneumons (Anthophorabia megachilis) were seen, which came forth as soon as the cells were opened."
The habits of the little blue or green Mason bees (Osmia) are quite varied. They construct their cells in the stems of plants, and in rotten posts and trees, or, like Andrena, they burrow in sunny banks. A European species selects snail shells for its nest, wherein it builds its earthen cells, while other species nidificate under stones. Curtis found two hundred and thirty cocoons of a British species (Osmia paretina), placed on the under side of a flat stone, of which one-third were empty. Of the remainder, the most appeared between March and June, males appearing first; thirty-five more bees were developed the following spring. Thus there were three successive broods, for three succeeding years, so that these bees lived three years before arriving at maturity. This may partly account for insect years, which are like "apple years," seasons when bees and wasps, as well as other insects, abound in unusual numbers.
Mr. G. R. Waterhouse, in the Transactions of the Entomological Society of London, for 1864, states that the cells of Osmia leucomelana "are formed of mud, and each cell is built separately. The female bee, having deposited a small pellet of mud in a sheltered spot between some tufts of grass, immediately begins to excavate a small cavity in its upper surface, scraping the mud away from the centre towards the margin by means of her jaws. A small, shallow mud-cup is thus produced. It is rough and uneven on the outer surface, but beautifully smooth on the inner. On witnessing thus much of the work performed, I was struck with three points: first, the rapidity with which the insect worked; secondly, the tenacity with which she kept her original position whilst excavating; and thirdly, her constantly going over work which had apparently been completed.... The lid is excavated and rendered concave on its outer or upper surface, and is convex and rough on its inner surface; and, in fact, is a simple repetition of the first-formed portion of the cell, a part of a hollow sphere."
The largest species of Osmia known to us is a very dark-blue species (O. lignivora). We are indebted to a lady for specimens of the bees with their cells, which had been excavated in the interior of a maple tree several inches from the bark. The bee had industriously tunnelled out this elaborate burrow (Fig. 26), and, in this respect, resembled the habits of the Carpenter bee more closely than any other species of its genus.
The tunnel was over three inches long, and about three-tenths of an inch wide. It contracted a little in width between the cell, showing that the bee worked intelligently, and wasted no more of her energies than was absolutely necessary. The burrow contained five cells, each half an inch long, being rather short and broad, with the hinder end rounded, while the opposite end, next to the one adjoining, is cut off squarely. The cell is somewhat jug-shaped, owing to a slight constriction just behind the mouth. The material of which the cell is composed is stout, silken, parchment-like, and very smooth within. The interstices between the cells are filled in with rather coarse chippings made by the bee.
The bee cut its way out of the cells in March, and lived for a month afterwards on a diet of honey and water. It eagerly lapped up the drops of water supplied by its keeper, to whom it soon grew accustomed, and seemed to recognize.
Our smallest and most abundant species is the little green Osmia simillima. It builds its little oval, somewhat urn-shaped cells against the roof of the large deserted galls of the oak-gall fly (Diplolepis confluentus), placing them, in this instance eleven in number, in two irregular rows, from which the mature bees issue through a hole in the gall (Fig. 27, with two separate cells). The earthen cells, containing the tough dense cocoons, were arranged irregularly so as to fit the concave vault of the larger gall, which was about two inches in diameter. On emerging from the cell the Osmia cuts out with its powerful jaws an ovate lid, nearly as large as one side of the cell.
In the Harris collection are the cells and specimens of Osmia pacifica, the peaceful Osmia, which, according to the manuscript notes of Dr. Harris, is found in the perfect state in earthen cells beneath stones. The cell is oval cylindrical, a little contracted as usual with those of all the species of the genus, thus forming an urn-shaped cell. It is half an inch long, and nearly three-tenths of an inch wide, while the cocoon, which is rather thin, is three-tenths of an inch long. We are not acquainted with the habits of the larva and pupa in this country, but Mr. F. Smith states that the larva of the English species hatches in eight days after the eggs are laid, feeds ten to twelve days, when it becomes full-grown, then spins a thin silken covering, and remains in an inactive state until the following spring, when it completes its transformations.
In the economy of our wild bees we see the manifestation of a wonderful instinct, as well as the exhibition of a limited reason. We can scarcely deny to animals a kind of reason which apparently differs only in degree from that of man. Each species works in a sphere limited by physical laws, but within that sphere it is a free agent. They have enough of instinct and reason to direct their lives, and to enable them to act their part in carrying out the plan of creation.
FOOTNOTES:
[Footnote 1: The cells are not perfectly hexagonal. See the studies on the formation of the cells of the bee, by Professor J. Wyman, in the Proceedings of the American Academy of Arts and Sciences, Boston, 1866; and the author's Guide to the Study of Insects, p 123.]
[Footnote 2: Notes on the Habits of the Humble Bee (Proceedings of the Essex Institute, vol. iv, 1864, p. 101).
Mr. Angus also writes us as follows concerning the habits of the Wandering Humble bee (Bombus vagans): "I have found the males plentiful near our garden fence, within a hole such as would be made by a mouse. They seem to be quite numerous. I was attracted to it by the noise they were making in fanning at the opening. I counted at one time as many as seven thus employed, and the sound could be heard several yards off. Several males were at rest, but mostly on the wing, when they would make a dash among the fanners, and all would scatter and play about. The workers seem to be of a uniform size, and full as large as the males. I think the object of the fanning was to introduce air into the nest, as is done by the Honey bees."]
[Footnote 3: "Since writing the above I have opened one of the new holes of Xylocopa, which was commenced between three and four weeks ago, in a pine slat used in the staging of the greenhouse. The dimensions were as follows:—Opening fully 3-8 wide; depth 7-16; whole length of tunnel 6 5-16 inches. The tunnel branched both ways from the hole. One end, from opening, was 2 5-8, containing three cells, two with larva and pollen, the third empty. The other side of the opening, or the rest of the tunnel, was empty, with the exception of the old bee (only one) at work. I think this was the work of one bee, and, as near as I can judge, about twenty-five days' work. Width of tunnel inside at widest 9-16 inch.
"I have just found a Xylocopa bobbing at one of the holes, and in order to ascertain the depth of the tunnel, and to see whether there were any others in them, I sounded with a pliable rod, and found others in one side, at a depth of five and one half inches; the other side was four inches deep without bees. The morning was cool, so that the object in bobbing could not have been to introduce fresh currents of air, but must have had some relation to those inside. Their legs on such occasions are, as I have noticed, loaded with pollen."]
CHAPTER II.
THE HOME OF THE BEES.
[Concluded.]
While the Andrena and Halictus bees, whose habits we now describe, are closely allied in form to the Hive bee, socially they are the "mud-sills" of bee society, ranking among the lowest forms of the family of bees. Their burrowing habits ally them with the ants, from whose nests their own burrows can scarcely be distinguished. Their economy does not seem to demand the exercise of so much of a true reasoning power and pliable instinct as characterizes bees, such as the Honey and Humble bee, which possess a high architectural skill. Moreover they are not social; they have no part in rearing and caring for their young, a fact that lends so much interest to the history of the Hive and Humble bee. In this respect they are far below the wasps, a family belonging next below in the system of Nature.
A glance at the drawing (Fig. 28), of a burrow, with its side galleries, of the Andrena vicina, reveals the economy of one of our most common forms. Quite early in spring, when the sun and vernal breezes have dried up the soil, and the fields exchange their rusty hues for the rich green verdure of May, our Andrena, tired of its idle life among the blossoms of the willow, the wild cherry, and garden flowers, suddenly becomes remarkably industrious, and wields its spade-like jaws and busy feet with a strange and unwonted energy. Choosing some sunny, warm, grassy bank (these nests were observed in the "great pasture" of Salem), not always with a southern exposure however, the female sinks her deep well through the sod from six inches to a foot into the sandy soil beneath. She goes to work literally tooth and nail. Reasoning from observations made on several species of wasps, and also from studying the structure of her jaws and legs, it is evident that she digs in and loosens the soil with her powerful jaws, and then throws out the dirt with her legs. She uses her fore legs like hands, to pass the load of dirt to her hind legs, and then runs backward out of her hole to dump it down behind her. Mr. Emerton tells me that he never saw a bee in the act of digging but once, and then she left off after a few strokes. He also says, "they are harmless and inoffensive. On several occasions I have lain on the grass near their holes for hours, but not one attempted to sting me; and when taken between the fingers, they make but feeble resistance."
To enter somewhat into detail, we gather from the observations of Mr. Emerton (who has carefully watched the habits of these bees through several seasons) the following account of the economy of this bee: On the 4th of May the bees were seen digging their holes, most of which were already two inches deep, and one, six inches. The mounds of earth were so small as to be hardly noticed. At this time an Oil beetle was seen prowling about the holes. The presence of this dire foe of Andrena at this time, it will be seen in a succeeding chapter on the enemies of the bees, is quite significant. By the 15th of May, hundreds of Andrena holes were found in various parts of the pasture, and at one place, in a previous season, there were about two hundred found placed within a small area. One cell was dug up, but it contained no pollen. Four days later, several Andrenas were noticed resting from their toil at the opening of their burrows. On the 28th of May, in unearthing six holes, eight cells were found to contain pollen, and in two of them a small larva. The pellets of pollen are about the size of a small pea. They are hard and round at first, before the young has hatched, but as the larva grows, the mass becomes softer and more pasty, so that the larva buries its head in the mass, and greedily sucks it in. When is the pollen gathered by the bee and kneaded into the pellet-like mass? On July 4th, a cell was opened in which was a bee busily engaged preparing the pollen, which was loosely and irregularly piled up, while there was a larva in an adjoining cell nearly half an inch long. It would seem, then, that the bee comes in from the fields laden with her stores of pollen, which she elaborates into bee bread within her cell.
When the bee returns to her cell she does not directly fly towards the entrance, since, as was noticed in a particular instance, she flew about for a long time in all directions without any apparent aim, until she finally settled near the hole, and walked into her subterranean retreat. On a rainy day, May 24th, our friend visited the colony, but found no bees flying about the holes. The little hillocks had been beaten down by the pitiless raindrops, and all traces of their industry effaced. On digging down, several bees were found, indicating that on rainy days they seek the shelter of their holes, and do not take refuge under leaves of the plants they frequent.
On the 29th of June, six full-grown larvae were exhumed, and one, about half grown. On the 20th of July, the colony seemed well organized, as, on laying open a burrow at the depth of six inches, he began to find cells. The upper ones, to the number of a dozen, were deserted and filled with earth and grass roots, and had evidently been built and used during the previous year. Below these were eight cells placed around the main vertical gallery, reaching down to the depth of thirteen inches, and all containing nearly full-grown larvae of the bees, or else those of some parasitic bee (Nomada) which had devoured the food prepared for the young Andrena.
About the first of August the larva transforms to a pupa or chrysalis, as at this time two pupae were found in cells a foot beneath the surface. As shown in the cut, those cells situated lowest down seem to be the last to have been made, while the eggs laid in the highest are the first to hatch, and the larvae disclosed from them, the first to change to pupae. Four days later the pupae of Cuckoo bees (Nomada) were found in the cells. No Andrenas were seen flying about at this time.
On the 24th of August, to be still very circumstantial in our narrative though at the risk of being tedious, three burrows were unearthed, and in them three fully formed bees were found nearly ready to leave their cells, and in addition several pupae. In some other cells there were three of the parasitic Nomada also nearly ready to come out, which seemed to be identical with some bees noticed playing very innocently about the holes early in the summer.
On the last day of August, very few of the holes were open. A number of Oil beetles were strolling suspiciously about in the neighborhood, and some little black Ichneumon flies were seen running about among the holes.
During mid-summer the holes were found closed night and day by clods of earth.
The burrow is sunken perpendicularly, with short passages leading to the cells, which are slightly inclined downwards and outwards from the main gallery. The walls of the gallery are rough, but the cells are lined with a mucous-like secretion, which, on hardening, looks like the glazing of earthenware. This glazing is quite hard, and breaks up into angular pieces. It is evidently the work of the bee herself, and is not secreted and laid on by the larva. The diameter of the interior of the cell is about one-quarter of an inch, contracting a little at the mouth. When the cell is taken out, the dirt adheres for a line in thickness, so that it is of the size and form of an acorn.
The larva of Andrena (Fig. 29) is soft and fleshy, like that of the Honey bee. Its body is flattened, bulging out prominently at the sides, and tapering more rapidly than usual towards each end of the body. The skin is very thin, so that along the back the heart or dorsal vessel may be distinctly seen, pulsating about sixty times a minute.
Our cut (Fig. 28, a) also represents the pupa, or chrysalis, as seen lying in its cell. The limbs are folded close to the body in the most compact way possible. On the head of the semi-pupa, i.e., a transition state between the larva and pupa, there are two prominent tubercles situated behind the simple eyes, or ocelli; these are deciduous organs, apparently aiding the insect in moving about its cell. They disappear in the mature pupa.
To those accustomed to rearing butterflies, and seeing the chrysalis at once assuming its perfected shape, after the caterpillar skin is thrown off, it may seem strange to hear one speak of a "half-pupa," and of stages intermediate between the larva and pupa. But the external changes of form, though rapidly passed through, consisting apparently of a mere sloughing off of the outer skin, are yet preceded by slow and very gradual alterations of tissues, resulting from the growth of cells. An inner layer of the larva-skin separates from the outer, and, by changes in the form of the muscles, is drawn into different positions, such as is assumed by the pupa, which thus lies concealed beneath the larva-skin. But a slight alteration is made in the general form of the larva, consisting mostly of an enlargement of the thoracic segments, which is often overlooked, even by the special student, though of great interest to the philosophic naturalist.
From Mr. Emerton's observations we should judge that the pupa state lasted from three to four weeks, as the larvae began to transform the first of August, and appeared during the last week of the same month as perfect bees.
The Andrena is seen as late as the first week in September, and again early in April, about the flowers of the willow. It is one of the largest of its genus and a common species.
Having, in a very fragmentary way, sketched the life history of our Andrena and had some glimpses of its subterranean life, let us now compare with it another genus of solitary bee (Halictus), quite closely allied in all respects, though a little lower in the scale.
The Halictus parallelus excavates cells almost exactly like those of Andrena; but since the bee is smaller, the holes are smaller, though as deep. Mr. Emerton found one nest in a path a foot in depth. Another nest, discovered September 9th, was about six inches deep. The cells are in form like those of Andrena, and like them, are glazed within. The egg is rather slenderer and much curved; in form it is long, cylindrical, obtuse at one end, and much smaller at the other. The larva (Fig. 31) is longer and slenderer, being quite different from the rather broad and flattened larva of Andrena. The body is rather thick behind, but in front tapers slowly towards the head, which is of moderate size. Its body is somewhat tuberculated, the tubercle aiding the grub in moving about its cell. Its length is nearly one-half (.40) of an inch. On the pupa are four quite distinct conical tubercles forming a transverse line just in front of the ocelli; and there are also two larger, longer tubercles, on the outer side of each of which, an ocellus is situated. Figure 30 represents the pupa seen from beneath.
Search was made on July 16th, where the ground was hard as stone for six inches in depth, below which the soil was soft and fine, and over twenty cells were dug out. "The upper cells contained nearly mature pupae, and the lower ones, larvae of various sizes, the smallest being hardly distinguishable by the naked eye. Each of these small larvae was in a cell by itself, and situated upon a lump of pollen, which was the size and shape of a pea, and was found to lessen in size as the larva grew larger. These young were probably the offspring of several females, as four mature bees were found in the hole." The larva of an English species hatches in ten days after the eggs are laid.
Another brood of bees appeared the middle of September, as on the ninth of that month (1864) Mr. Emerton found several holes of the same species of bee, made in a hard gravel road near the turnpike. When opened, they were found to contain several bees with their young. September 2nd, of this year, the same kind of bee was found in holes, and just ready to leave the cell. It is probable that these bees winter over.
We have incidentally noticed the presence in the nests of Andrena and Halictus of a stranger bee, clad in gay, fantastic hues, which lives a parasitic life on its hosts. This parasitism does not go far enough to cause the death of the host, since we find the young of the parasitic Cuckoo bee, in cells containing the young of the former.
Mr. F. Smith, in his "Catalogue of British Bees," says of this genus: "No one appears to know anything beyond the mere fact of their entering the burrows of Andrenidae and Apidae, except that they are found in the cells of the working bees in their perfect condition: it is most probable that they deposit their eggs on the provision laid up by the working bee, that they close up the cell, and that the working bee, finding an egg deposited, commences a fresh cell for her own progeny."
He has, however, found two specimens of Nomada, sexfasciata in the cells of the long-horned bee, Eucera longicornis. He also states, that while some species are constant in their attacks on certain Halicti and Andrenae, others attack different species of these genera indiscriminately. In like manner another Cuckoo bee (Coelioxys) is parasitic on Megachile and Saropoda; Stelis is a parasite on Osmia, the Mason bee: and Melecta infests the cells of Anthophora.
The observations of Mr. Emerton enable us still further to clear up the history of this obscure visitor. He found both the larva and pupa, as well as the perfect bee, in the cells of both genera; so that either both kinds of bee, when hatched from eggs laid in the same cell, feed on the same pollen mass, which therefore barely suffices for the nourishment of both; or the hostess, discovering the strange egg laid, cuckoo-like, in her own nest, has the forethought to deposit another ball of pollen to secure the safety of her young.
Is such an act the operation of a blind instinct? Does it not rather ally our little bee with those higher animals which undoubtedly possess a reasoning power? Its instinct teaches it to build cells, and prepare its pollen mass, and lay an egg thereon. Its reason enables it, in such an instance as this, when the life of the brood is threatened, to guard against any such danger by means to which it does not habitually resort. This instance is paralleled by the case of our common summer Yellow bird, which, on finding an egg of the Cow bunting in its nest, often builds a new nest above it, to the certain destruction of the unwelcome egg in the nest beneath.
In the structure of the bee, and in all its stages of growth, our parasite seems lower in the zooelogical scale than its host. It is structurally a degraded form of Working-bee, and its position socially is unenviable. It is lazy, not having the provident habits of the Working-bees; it aids not in the least, so far as we know, the cross-fertilization of plants—one great office in the economy of nature which most bees perform,—since it is not a pollen-gatherer, but on the contrary is seemingly a drag and hinderance to the course of nature. But yet nature kindly, and as if by a special interposition, provides for its maintenance, and the humble naturalist can only exclaim, "God is great, and his ways mysterious," and go on studying and collecting facts, leaving to his successors the more difficult task, but greater joy of discovering the cause and reason of things that are but a puzzle to the philosophers of this day.
The larva of Nomada may be known from those of its host, by its slenderer body and smaller head, while the body is smoother and more cylindrical. Both sexes of Nomada imbricata and N. pulchella were found by Mr. Emerton, the former in both the Andrena and Halictus nests, and both were found in a single Andrena nest.
CHAPTER III.
THE PARASITES OF THE HONEY BEE.
Very few bee-keepers are probably aware how many insect parasites infest the Honey bee. In our own literature we hear almost nothing of this subject, but in Europe much has been written on bee parasites. From Dr. Edward Assmuss' little work on the "Parasites of the Honey Bee," we glean some of the facts now presented, and which cannot fail to interest the general reader as well as the owner of bees.
The study of the habits of animal parasites has of late gained much attention among naturalists, and both the honey and wild bees afford good examples of the singular relation between the host and the parasites which live upon it. Among insects generally, there are certain species which devour the contents of the egg of the victim. Others, and this is the most common mode of parasitism, attack the insect in its larva state; others, in the pupa state, and still others in the perfect, or imago state. Dr. Leidy has shown that the wood-devouring species of beetle, Passalus cornutus, and some Myriopods, or "thousand legs," are, in some cases, tenanted by myriads of microscopic plants and worms which luxuriate in the alimentary canal, while the "caterpillar-fungus" attacks sickly caterpillars, filling out their bodies, and sending out shoots into the air, so that the insect looks as if transformed into a vegetable.
The Ichneumon flies, of which there are undoubtedly several thousand species in this country, are the most common insect parasites. Next to these are the different species of Tachina and its allied genera. These, like Ichneumons, live in the bodies of their hosts, consuming the fatty parts, and finishing their transformations just as the exhausted host is ready to die, issue from their bodies as flies, closely resembling the common housefly.
A small fly has been found in Europe to be the most formidable foe of the hive bee, sometimes producing the well-known disease called "foul-brood," which is analogous to the typhus fever of man.
This fly, belonging to the genus Phora (Fig. 32, Phora incrassata; a, larva; b, puparium; c, another species from Mammoth Cave), is a small insect about a line and a half long, and found in Europe during the summer and autumn flying slowly about flowers and windows, and in the vicinity of beehives. Its white, transparent larva is cylindrical, a little pointed before, but broader behind. The head is small and rounded, with short, three-jointed antennae, and at the posterior end of the body are several slender spines. The puparium, or pupa case, inclosing the delicate chrysalis, is oval, consisting of eight segments, flattened above, with two large spines near the head, and four on the extremity of the body.
When impelled by instinct to provide for the continuance of its species, the Phora enters the beehive and gains admission to a cell, when it bores with its ovipositor through the skin of the bee larva, laying its long oval egg in a horizontal position just under the skin. The embryo of the Phora is already well developed, so that in three hours after the egg is inserted in the body of its unsuspecting and helpless host, the embryo is nearly ready to hatch. In about two hours more it actually breaks off the larger end of the egg-shell and at once begins to eat the fatty tissues of its victim, its posterior half still remaining in the shell. In an hour more, it leaves the egg entirely and buries itself completely in the fatty portion of the young bee.
The maggot moults three times. In twelve hours after the last moult it turns around with its head towards the posterior end of the body of its host, and in another twelve hours, having become full-fed, it bores through the skin of the young, eats its way through the brood-covering of the cell and falls to the bottom of the hive, where it changes to a pupa in the dust and dirt, or else creeps out of the door and transforms in the earth. Twelve days after, the fly appears.
The young bee, emaciated and enfeebled by the attacks of its ravenous parasite, dies, and its decaying body fills the bottom of the cell with a slimy, foul-smelling mass, called "foul-brood." This gives rise to a miasma which poisons the neighboring brood, until the contagion (for the disease is analogous to typhus, jail or ship-fever) spreads through the whole hive, unless promptly checked by removing the cause and thoroughly cleansing the hive.
Foul-brood sometimes attacks our American hives, and, though the cause may not be known, yet from the hints given above we hope to have the history of our species of Phora cleared up, should our disease be found to be sometimes due to the attacks of such a parasitic fly.
We figure the Bee louse of Europe (Fig. 33 b, Braula caeca), which is a singular wingless spider-like fly, allied to the wingless Sheep tick (Melophagus), the wingless Bat tick (Nycteribia) and the winged Horse fly (Hippobosca). The head is very large, without eyes or ocelli (simple eyes), while the ovate hind-body consists of five segments, and is covered with stiff hairs. It is one-half to two-thirds of a line long. This spider fly is "pupiparous," that is, the young, of which only a very few are produced, is not born until it has assumed the pupa state or is just about to do so. The larva (Fig. 33 a) is oval, eleven-jointed, and white in color. The very day it is hatched, it sheds its skin and changes to an oval puparium of a dark brown color.
Its habits resemble those of the flea. Indeed, should we compress its body strongly, it would bear a striking resemblance to that insect. It is evidently a connecting link between the flea, and the two winged flies. Like the former it lives on the body of its host, and obtains its food by plunging its stout beak into the bee and sucking its blood.
It has not been noticed in this country, but is liable to be imported on the bodies of Italian bees. Generally, one or two of the Braulas may, on close examination, be detected on the body of the bee; sometimes the poor bees are loaded down by as many as a hundred of these hungry blood-suckers. Assmuss recommends rubbing them off with a feather, as the bee goes in and out of the door of its hive.
Among the beetles are a few forms occasionally found in bees' nests and also parasitic on the body of the bee. Trichodes apiarius (Fig. 34, a, larva; b, pupa, front view) has long been known in Europe to attack the young bees. In its perfect, or beetle state it is found on flowers, like our Trichodes Nuttallii, which is commonly found on the Spiraea in August, and which may yet prove to enter our beehives. The larva devours the brood, but with the modern hive its ravages may be readily detected.
The Oil beetle, Meloe angusticollis (Fig. 35, male, differing from the female by having the antennae as if twisted into a knot; Fig. 36, the active larva found on the body of the bee), is a large dark blue insect found crawling in the grass in the vicinity of the nests of Andrena, Halictus, and other wild bees in May, and again in August and September. The eggs are laid in a mass covered with earth at the root of some plant. During April and early in May, when the willows are in blossom, we have found the young recently hatched larvae in considerable abundance creeping briskly over the bees, or with their heads plunged between the segments of the body, greedily sucking in the juices of their host. Those that we saw occurred on the Humble and other wild bees, and on various flies (Syrphus and Muscidae), and there is no reason why they should not infest the Honey bee, which frequents similar flowers, as they are actually known to do in Europe. These larvae are probably hatched out near where the bees hibernate, so as to creep into their bodies before they fly in the spring, as it would be impossible for them to crawl up a willow tree ten feet high or more, their feet being solely adapted for climbing over the hairy body of the bee, which they do not leave until about to undergo their strange and unusual transformations.
In Europe, Assmuss states that on being brought into the nest by the bee, they leave the bee and devour the eggs in the bee cells, and then attack the bee bread. When full-fed and ready to pass through their transformations to attain the beetle state, instead of at once assuming the pupa and imago forms, as in the Trichodes represented in fig. 34, they pass through a hyper-metamorphosis, as Fabre, a French naturalist, calls it. In other words, the changes in form which are preparatory to assuming the pupa and imago states are more marked and almost coequal with the larva and pupa states, so that the Meloe, instead of passing through three states (the egg, larva and pupa), in realty passes through these and two others in addition, which are intermediate. The whole subject of the metamorphosis of this beetle needs revision, but Fabre states that the larva, soon after entering the nest of its host, changes its skin and assumes a second larva form. Newport, who with Siebold has carefully described the metamorphoses of Meloe, does not mention this stage in its development, which Fabre calls "pseudo-chrysalis." It is motionless, the head is mask-like, without movable appendages, and the feet are represented by six tubercles. This is more properly speaking the semi-pupa, and the mature pupa grows beneath its mask-like form, which is finally moulted. This form, however, according to Fabre, changes its skin and turns into a third larva form (Fig. 37). After some time it assumes its true pupa form (Fig. 38), and finally moults this skin to appear as a beetle.
Fabre has also, in a lively and well-written account, given a history of Sitaris, a European beetle, somewhat resembling Meloe. He states that Sitaris lays its eggs near the entrance of bees' nests, and at the very moment that the bee lays her egg in the honey cell, the flattened, ovate Sitaris larva drops from the body of the bee upon which it has been living, and feasts upon the contents of the freshly laid egg. After eating this delicate morsel it devours the honey in the cells of the bee and changes into a white, cylindrical, nearly footless grub, and after it is full-fed, and has assumed a supposed "pupa" state, the skin, without bursting, incloses a kind of hard "pupa" skin, which is very similar in outline to the former larva, within whose skin is found a whitish larva which directly changes into the true pupa. In a succeeding state this pupa in the ordinary way changes to a beetle which belongs to the same group of Coleoptera as Meloe. We cannot but think, from observations made on the humble bee, the wasp, two species of moths and several other insects, that this "hyper-metamorphosis" is not so abnormal a mode of insect metamorphosis as has been supposed, and that the changes of these insects, made beneath the skin of the mature larva before assuming the pupa state, are almost as remarkable as those of Meloe and Sitaris, though less easily observed than they. Several other beetles allied to Meloe are known to be parasitic on wild bees, though the accounts of them are fragmentary.
THE STYLOPS PARASITE.
The history of Stylops, a beetle allied to Meloe, is no less strange than that of Meloe, and is in some respects still more interesting. On June 18th I captured an Andrena vicina which had been "stylopized." On looking at my capture I saw a pale reddish-brown triangular mark on the bee's abdomen; this was the flattened head and thorax of a female Stylops (Fig. 39a, position of the female of Stylops, seen in profile in the abdomen of the bee; Fig. 39b, the female seen from above. The head and thorax are soldered into a single flattened mass, the baggy hind-body being greatly enlarged like that of the gravid female of the white ant, and consisting of nine segments).
On carefully drawing out the whole body (Pl. 1, Fig. 6, as seen from above, and showing the alimentary canal ending in a blind sac; Fig. 6a, side view), which is very extensible, soft and baggy, and examining it under a high power of the microscope, we saw multitudes, at least several hundred, of very minute larvae, like particles of dust to the naked eye, issuing in every direction from the body of the parent now torn open in places, though most of them made their exit through an opening on the under side of the head-thorax. The Stylops, being hatched while still in the body of the parent, is, therefore viviparous. She probably never lays eggs.
On the last of April, when the Mezereon was in blossom, I caught the singular looking male (Stylops Childreni, Fig. 40; a, side view; it is about one-fourth of an inch long), which was as unlike its partner as possible. I laid it under a tumbler, when the delicate insect flew and tumbled about till it died of exhaustion in a few hours.
It appears, then, that the larvae are hatched during the middle or last of June from eggs fertilized in April. The larvae then crawl out upon the body of the bee, on which they are transported to the nest, where they enter, according to Peck's observations, the body of the larva, on whose fatty parts they feed. Previous to changing to a pupa the larva lives with its head turned towards that of its host, but before assuming the perfect state (which they do in the late summer or autumn) it must reverse its position. The female protrudes the front part of her body between the segments of the abdomen of her host, as represented in our figure. This change, Newport thinks, takes place after the bee-host has undergone its metamorphoses, though the bee does not leave her earthen cells until the following spring. Though the male Stylops deserts his host, his wingless partner is imprisoned during her whole life within her host, and dies immediately after giving birth to her myriad (for Newport thinks she produces over two thousand) offspring.
Xenos Peckii, an allied insect, was discovered by Dr. Peck to be parasitic in the body of wasps, and there are now known to be several species of this small but curious family, Stylopidae, which are known to live parasitically on the bodies of our wild bees and wasps. The presence of these parasites finally exhausts the host, so that the sterile female bee dies prematurely.
As in the higher animals, bees are afflicted with parasitic worms which induce disease and sometimes death. The well-known hair worm, Gordius, is an insect parasite. The adult form is about the size of a slender knitting needle, and is seen in moist soil and in pools. It lays, according to Dr. Leidy, "millions of eggs connected together in long cords." The microscopical, tadpole-shaped young penetrate into the bodies of insects frequenting damp localities. Fairly ensconced within the body of their unsuspecting host, they luxuriate on its fatty tissues, and pass through their metamorphoses into the adult form, when they desert their living house and take to the water to lay their eggs. In Europe, Siebold has described Gordius subbifurcus, which infests the drones of the Honey bee, and also other insects. Professor Siebold has also described Mermis albicans, which is a similar kind of hair worm, from two to five inches long, and whitish in color. This worm is also found, strangely enough, only in the drones, though it is the workers which frequent watery places to appease their thirst.
Thousands of insects are carried off yearly by parasitic fungi. The ravages of the Muscardine, caused by a minute fungus (Botrytris Bassiana), have threatened the extinction of silk culture in Europe, and the still more formidable disease called pebrine is thought to be of vegetable origin. Dr. Leidy mentions a fungus which must annually carry off myriads of the Seventeen Year Locust. A somewhat similar fungus, Mucor mellitophorus (Fig. 41), infests bees, filling the stomach with microscopical colorless spores, so as greatly to weaken the insect.
As there is a probability that many insects, parasites on the wild bees, may sooner or later afflict the Honey bee, and also to illustrate farther the complex nature of insect parasitism, we will for a moment look at some other bee parasites.
Among the numerous insects preying in some way upon the Humble bee are to be found other species of bees and moths, flies and beetles. Insect parasites often imitate their host: Apathus (Plate I, Fig. 1, A. Ashtoni) can scarcely be distinguished from its host, and yet it lives cuckoo-like in the cells of the Humble bee, though we know not yet how injurious it really is. Then there are Conops and Volucella, the former of which lives like Tachina and Phora within the bee's body, while the latter devours the brood. The young (Plate I, Figs. 5, 5a) of another fly allied to Anthomyia, of which the Onion fly (Fig. 42) is an example, is also not unfrequently met with. A small beetle (Plate 1. Fig. 4, Antherophagus ochraceus) is a common inmate of Humble bees' nests, and probably feeds upon the wax and pollen. We have also found several larvae (Fig. 43) of a beetle of which we do not know the adult form. Of similar habits is probably a small moth (Nephopteryx Edmandsii, Plate I, Figs. 2; 2a, larva; Fig. 2b, chrysalis, or pupa) which undoubtedly feeds upon the waxen walls of the bee cells, and thus, like the attacks of the common bee moth (Galleria cereana, whose habits are so well known as not to detain us, must prove very prejudicial to the well being of the colony. This moth is in turn infested by an Ichneumon fly (Microgaster nephoptericis, Plate I, Figs. 3, 3a) which must prove quite destructive. |
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