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OUR COMMON INSECTS.
[Illustration: AMERICAN SILK WORM (MALE).]
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 antennæ, a pair of jaws
(mandibles), and two pairs of maxillæ, 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
antennæ, and the second maxillæ, 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.
[Illustration: 1. Spider (Tegenaria).]
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
larvæ, 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.
[Illustration: 2. Centipede.]
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 tracheæ, 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.
[Illustration: 3. Caudal appendage of larva of Agrion.]
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.
[Illustration: 4. Different forms of jaws.]
[Illustration: 5. Mouth parts of the Larva of a Beetle.]
[Illustration: 6. Maxilla of a Beetle.]
_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 (maxillæ, Fig. 5, _a_, upper, b, under side of
the head of a young beetle; _at_, antennæ, _md_, mandible, _mx_,
maxillæ, _mx_[1], labium) and the feelers (palpi) attached to the
maxillæ, 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
maxillæ 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.)
[Illustration: 7. Mouth parts of a Humble Bee.]
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.
[Illustration: 8. Larva of a beetle (Photuris).]
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 tracheæ), 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
(tracheæ) 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.
[Illustration: 9. Figure cut by an insect's wing.]
[Illustration: 10. Figure cut by a bird's wing.]
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.
[Illustration: 11. Trajectory of an insect's wing.]
[Illustration: 12. Trajectory of a bird's wing.]
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.
[Illustration: 13. A bird on the wing.]
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 Müller, 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 antennæ 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 antennæ, 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 Lespès, a Swiss anatomist, in his remarks on the auditory sacs,
which he says are found in the antennæ 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.
[Illustration: 14. _a_ Larva, _b_ chrysalis of a 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.
[Illustration: 15. Imago or adult Butterfly.]
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 larvæ and pupæ
of insects, and under what different guises insects live in their early
stages.
[Illustration: Larva, pupa, and adult of a Leaf Beetle (Galeruca).]
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 larvæ 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. Guérin 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.
[Illustration: 15. Cell and Eggs of Bombus.]
"As soon as the larvæ 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 larvæ 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 larvæ. 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.
[Illustration: 16. Meloë.]
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 larvæ 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 larvæ 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 Meloë
(Fig. 16), Stylops (Fig. 17, male; 18_b_, female; _a_, position in the
body of its host), and Antherophagus prey upon them.
[Illustration: 17. Male Stylops.]
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 larvæ 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.
[Illustration: 18. Female Stylops.]
[Illustration: 19. Carpenter Bee.]
"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.
[Illustration: 20. Larva and Pupa of Anthrax.]
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.
[Illustration: 21. Nest of Carpenter Bee.]
At the time of opening the burrow, July 8th, the cells contained nearly
full-grown larvæ, 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 larvæ (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.
[Illustration: 22. Nest of Ceratina.]
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.
[Illustration: 23. Larva of Ceratina.]
[Illustration: 24. Nest of Tailor Bee.]
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.
[Illustration: 25. Tailor Bee.]
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.
[Illustration: 26. Nest of Osmia.]
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.
[Illustration: 27. Nest of Osmia in a gall.]
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.
[Illustration: Paper Wasp.]
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."]