in the structure of the mechanism by which the males make the trilling
sound for which they have been so long famous. In the male of the
Seventeen-year Cicada the musical instrument consists of two stretched
membranes, one on each side of the body, which are plainly to be
seen immediately behind the wings. These membranes are gathered into
numerous fine plaits, and are played upon by muscles or cords fastened
to their under surfaces. When these muscles contract and relax, which
they do with great rapidity, the drum-heads, which the membranes
resemble, are alternately tightened and loosened, the effect of this
alternate tension and relaxation being the production of a rattling
sound very much like that caused by a succession of quick pressures
upon a slightly complex and elastic piece of tin-plate. Certain
cavities within the body of the insect, which may be seen on raising
two large valves beneath the abdomen, and which are separated from
each other by thin transparent partitions of the brilliancy of mica or
highly polished glass, tend to increase the intensity of the sound.
In the winged state _Cicada septendecim_, as the subject of our
sketch was named by the immortal Linnæus, is of a black color, with
transparent wings and wing-covers, the thick anterior edge and veins of
which being orange-red. Near the tips of the latter there is a dusky
zig-zag line which resembles in shape the letter W. The eyes, when
living, are also red, while the legs are a dull orange, which color is
conspicuous along the edges of the rings of the body. The wings expand
from two and a half to three and a quarter inches.
[Illustration: SEVENTEEN-YEAR CICADA.
Adult, Chrysalis-Case, Pupa, Entrances to Burrows and Egg-Nests.]
About the middle of June the perfect insects make their appearance, and
as they generally come in large numbers they do a great deal of damage.
In some localities they congregate to such an extent upon the trees as
to bend and even to break down the limbs by their weight. The din of
their discordant drums resounds in the woods and orchards from morning
to evening. As their life is of rather short duration, not lasting for
a longer period than a month, they soon begin to pair, and it is not
long afterwards that the females may be seen preparing nests for the
reception of their eggs. Branches of moderate size are selected for
this purpose. Their manner of perforation is curious and interesting.
Clasping the branch on both sides with their legs, and bending the
ovipositor at an angle of forty-five degrees, they repeatedly thrust it
into the bark and wood in the direction of the fibres, at the same time
setting the lateral saws at work, thereby detaching little splinters
of wood at one end, which are intended to serve as a kind of fibrous
cover for the nest. The hole is bored obliquely to the pith, and by a
repetition of the same operation is gradually enlarged until is formed
a longitudinal fissure of sufficient extent to receive from ten to
twenty eggs. The side-pieces of the piercer act as a groove to convey
the eggs to the nest, where they are deposited in pairs, but separated
from each other by a narrow strip of wood. When two eggs have been
thus placed, the piercer is withdrawn for a moment, and then inserted
till two more eggs are dropped in a line with the first, and thus the
operation is repeated until the fissure has been filled, when the
insect removes to a little distance and commences to make another nest
to contain two more rows of eggs. It takes about fifteen minutes to
prepare a groove and fill it with eggs. As many as twenty grooves are
sometimes made in a branch by a single insect, and when the limb has
been sufficiently stocked she goes from it to another, or from tree to
tree, until she has got rid of her complement of from five hundred to
seven hundred eggs. So weak does she at length become, in her continued
endeavor to provide for the succession of her race, as to fall, in an
attempt to fly, an almost lifeless lump to the earth, where her spirit
soon goes out never more to enliven its frail house of clay.
Although Cicadas abound most upon the oaks, yet there seem to be no
trees or shrubs that are exempt from their attacks, unless it be the
various species of pines and firs. The punctured limbs languish and
die soon after the eggs are laid, and as often happens are broken off
by the winds; but when this is the case the eggs never hatch, for
the moisture of the living branch seems necessary for their proper
development.
The eggs are one-twelfth of an inch in length, and one-sixteenth of
an inch through the middle, but taper to an obtuse point at each end.
They are of a pearl-white color. The shell is so thin and delicate that
the form of the inclosed insect can be seen before the egg is hatched.
One writer claims that fifty-two days, and others that fourteen days,
constitute the period required for the hatching of the egg.
When it bursts the shell the young insect is one-sixteenth of an inch
long, and is of a yellowish-white color, excepting the eyes and
the claws of the fore-legs, which are reddish. It is clothed with
small hairs. In form it is grub-like, larger proportionally than the
parent, and provided with six legs, the first pair being very large,
shaped like lobster-claws, and armed beneath with strong spines.
Little prominences take the place of wings, and under the breast is
a long beak for suction. Its movements, after leaving the egg, are
very lively, and nearly as quick as some of the ants. But after a few
moments their instincts prompt them to reach the ground. They do not
attain this end by descending the body of the tree, nor by casting
themselves off precipitately, but, running to the side of the limb,
deliberately loosen their hold and drop to the ground, making the
perilous descent with the utmost safety. This seems almost incredible,
but it has been repeatedly observed by scores of honest witnesses.
[Illustration: NEW-BORN CICADA.
Line Below Shows Natural Size.]
On reaching the ground the young insects immediately burrow their
way into the soil, using their broad and strong fore-feet pretty
much after the fashion of the mole. They apparently follow, in their
descent, the roots of plants, fastening their beaks into the most
tender and succulent, and thus imbibing their juices, which constitute
their sole aliment. They do not descend very deeply into the ground,
probably not more than ten or twelve inches, although accounts have
been published of their discovery at a depth of ten or twelve feet, but
their occurrence at such great distances from the top of the ground is
doubtless the result of accident.
The only alteration to which the insects are subject during the
seventeen years of their subterranean confinement, is an increase in
size, and the more complete development of the four small scale-like
prominences of the back, which contain their future wings.
When the time of its transformation draws near, the larva, in which
stage the insect passes the greater part of its existence, works its
way up towards the surface, oftentimes in a very circuitous manner,
for local changes make it necessary for it to bore through hard woods
and between stones well beaten down. The burrow which it thus produces
is cylindrical, about five-eighths of an inch in diameter, and firmly
cemented and varnished so as to be water-proof. The upper portion, to
the extent of five or six inches, is empty, and serves as a habitation
till the period of its exit arrives, while the lower is filled with
earthy matter removed by the insect in its progress. In this cell it
remains during several days, ascending to the top for the benefit of
the sunshine and air when the weather is auspicious, even venturing to
peep forth occasionally, but descending on the occurrence of cold or
wet weather. But when the favorable moment to leave their subterranean
retreats arrives, the Cicada-grubs, or more properly pupæ, for such
they are now to be considered, although they still retain something
of the grub-like form, issue from the ground in great numbers as
evening draws on, crawl up the trunks of trees, the stems of herbaceous
plants, or on to whatever is convenient, which they grasp securely
with their claws. After resting awhile, their skins, which have become
dry and of an amber color, are by repeated exertions rent along the
back, and through the slit formed the included Cicada pushes its
head and body, and withdraws its wings and legs from their separate
cases, and, crawling to a short distance, leaves its empty pupa-case
fastened to the tree. At first the wing-covers and wings are small and
opaque, but in a few hours they acquire their natural size and shape.
It is not, however, for three or four days that the muscles harden
sufficiently for them to assume their characteristic flight. The males
make their appearance some days in advance of the females, and also
disappear sooner. During several successive nights the pupæ continue
to issue from the ground, and in some places, as was the case in May
of 1868, when these insects appeared in great numbers in the vicinity
of Philadelphia, the whole surface of the soil was made by their
operations to assume a honey-combed appearance.
[Illustration: DOME-LIKE HOUSE OF CICADA.
Longitudinal Section Showing Pupa in Two Positions.]
In localities where the soil is low and swampy, a remarkable chamber is
built up by the larva, where the pupa may be found awaiting the time
of its change to the winged state. These chambers were first noticed
by S. S. Rathvon, at Lancaster, Pa., and are from four to six inches
above the ground, and have a diameter of one inch and a quarter. When
ready to emerge the insect backs down to an opening which is left in
the side of the structure on a level with the surface of the ground,
issues forth and undergoes its transformation in the usual manner.
This peculiar habit of nest-building, which is so unlike what is
customary with the Cicadidæ, or with Hemiptera in general, points to a
high degree of intelligence among these insects, showing a remarkable
ability to adapt themselves to environing circumstances. Undue moisture
would be prejudicial to the pupa, as the larva seemed to know, through
the guidance of the same dumb and unerring instinct which teaches it to
cement its underground dwelling, but would that same instinct teach it
to construct so wonderful a dome-like house as the one described for
the preservation of its after-life, and one so eminently fitted by its
position, shape, size and entrance to secure the necessary shelter,
warmth and air for its protection and development? I apprehend not.
Nothing short of a reason, similar to that in man, but differing in
degree, would enable it to grasp the situation in which it found itself
to be placed when nearing its final change, and plan with the view of
carrying out the ultimate aim of its existence.
Fortunately, these insects are appointed to return at periods so
distant that vegetation has a chance to recover from the injuries which
they inflict. Were they to appear at shorter intervals, our forest- and
fruit-trees would be entirely destroyed by them. They are, moreover,
subject to many accidents, and have many enemies, which contribute to
diminish their numbers. Their eggs are eaten by birds, and the young,
when they leave the egg, are preyed upon by ants, who mount the trees
for that purpose, or take them upon the ground as they are about to
enter upon their protracted larval career. Blackbirds eat them in the
spring when turned up by the plough, and hogs, when allowed to run at
large in the woods, root them up and devour large numbers, especially
just before the arrival of the period of their final transformation,
when they are lodged only a few inches below the surface of the soil.
Many perish in the egg by the closing up of the bark and wood that
constitute the walls of the perforations, thus burying the eggs before
they have hatched, and others, no doubt, are killed by their perilous
descent from the trees.
As its name implies, this insect generally requires seventeen years
to complete its transformations, a fact that was first pointed out
many years ago by the botanist Kalm. The late Prof. Riley, who had
given this species a great deal of study, was the first to work
out the problem of its periodical returns. He found that there are
also thirteen-year broods, and that both sometimes occur in the same
locality, but that in general terms the thirteen-year brood might be
called the southern form, and the seventeen-year the northern form. At
the limits of their respective ranges these broods overlap each other.
The shorter-lived form he named provisionally _Cicada tredecim_. It
was the existence of this brood that led entomologists to doubt the
propriety of Linné’s name, because, in calculating each appearance
as occurring in any locality at the end of every seventeen years,
they could not make the dates of its periodical returns correct. But
it was Prof. Riley that cleared up the matter. It happened in the
summer of 1868 that one of the largest seventeen-year broods occurred
simultaneously with one of the largest thirteen-year broods. Such
an event, so far as these two particular broods are concerned, has
not taken place since 1647, nor will it take place again till the
year 2089. There are absolutely no specific differences between the
two broods other than in the time of maturing. There is, however, a
dimorphous form that appears with both these broods. It is smaller,
of a much darker color, has an entirely different voice, appears a
fortnight sooner, and is never known to pair with the ordinary form.
Dr. J. C. Fisher, in 1851, described it as _Cicada cassinii_, but the
specific differences are not sufficiently well defined to entitle it to
rank as a species.
HONEY-DEW.
That aphides secrete, or rather excrete, a saccharine fluid, called
honey-dew, which constitutes an important part of the food of ants,
is a fact well known to naturalists. It must not be supposed,
however, that this was its primitive use. But that it is in some way
connected with the preservation of the tender creatures by which it is
elaborated, there can exist not the slightest doubt.
Concerning its origin and application, and the benefit which it secures
to its authors, various opinions have been hazarded, but they have all
been too unsatisfactory to merit more than a passing notice. That it
was of some advantage to young aphides was surmised by many, but the
proofs necessary to sustain such a surmise were unfortunately wanting.
It was left to the latter half of the nineteenth century to throw
correct light upon the subject.
Whilst engaged some few years ago in the study of the species that
affects the blossoms of one of our gourds--the _Cucurbita ovifera_ of
botanists--certain phenomena were observed, which promised an easy and
speedy solution of the problem.
Gathered in compact masses, like companies of soldiery preparing for
a foray, hundreds of aphides were seen, busily feeding, all over the
flowers. There were old and young, not an indiscriminate mingling of
ages and sizes, but an orderly arrangement of families, each family
preceded by its own appropriate head. First came the very young of
each family, only to be followed by those that were older, leaving the
oldest of all to lead up the rear.
[Illustration: BLOSSOM OF CUCURBITA.
Mother-Aphis and Her Army of Children on Tube.]
Here, it was apparent, was a most wonderful manifestation of
intelligent design. The newly-born, needing the mother’s earliest
attention, were in closest proximity, while the almost mature were the
farthest removed from her essential presence.
All this seemed to indicate the dearest relationship subsisting between
mother and offspring, but judging from outward appearances, little,
if any, love existed. It is true that maternal instinct, which is
seldom so far gone as to shut its ears to the beseechings of suffering
offspring for food, was far from being absent. Instances of its
presence were momentarily noted.
But a stimulus seemed, in some cases, quite necessary to its
manifestation. There were times when the honey-glands acted without
any provocation. It was only, however, when the very tender were
a-hungry, that pressure was brought to bear upon the mothers. A few
gentle reminders served to arouse them from the apathetic indifference
which possessed them. The antennæ of the young were the means employed
for this purpose. Two or three caresses almost immediately brought
a discharge of honey. Again and again was the process observed, and
always with the same invariable result.
Never for a longer period than two days were the very young dependent
upon this manner of feeding, for their digestive organs were too weak
and delicate to assimilate earlier, without injury, the powerful juices
of the food-plant.
But what of the older offspring? That they were far from being
disregarded by parental provision, subsequent developments only too
plainly showed. The excretion, though less urgent in their case than
in that of the very young, was quite as indispensable. Were it not so,
what reason can be assigned for their very strict adherence to the
course over which the maternal head had already passed in feeding?
From what has been said, there can be no doubt that the newly-born
aphis derives material advantage from the excretion. But as the supply
is clearly above the requirements, why the excess? It is evident
nature does not need it as a kind of compensation for losses sustained
through aphides. Then what purpose does it serve? It becomes in part
the pabulum of the stronger of the young, and this it accomplishes by
mixing with the natural juices of the plant, thereby rendering them fit
for use.
To serve as food for the young is then the primary object of
aphis-excretion. That a secondary purpose, namely, the preservation of
the species, is also subserved, there can be no question. How this is
effected, it shall now be my endeavor to show.
Ants, it is well known, are fond of sugar, gums and saccharine
solutions, as well as the rich juices and tender tissues of animals.
But their appetite for sweets is stronger than for all other diets.
To them aphis would prove quite as toothsome a morsel as it is to
Coccinella, and would be as eagerly hunted for by them were it not for
this matter of sweets.
Way back in the history of time, things were perhaps different from
what they are now. Aphis was then a racy tidbit, and shared, no doubt,
the murderous assaults of Formica, as it did of other carnivores.
For ages this may have been going on, but how long conjecture only can
tell. But there came a time when affairs were changed. A new order
of things was initiated. Earth was growing better and impressing new
features upon its life. An Ant, more wise than any of its fellows, or
any that had ever lived before, doubtless stepped upon the scene, and a
new era for Aphis inaugurated.
Finding by accident, or otherwise, the delightful qualities of
aphis-excretion, it would not be slow to communicate the information to
its companions. And as news travels rapidly, and ants are by no means
reticent creatures, but a short time would be necessary to carry it
everywhere, till all the families, near and remote, of the great world
of the Formicidæ would be made acquainted with the important discovery.
Now, as ants are endowed with a high degree of intelligence,
considering the position they occupy in the grand scale of created
existences, they would soon perceive that their highest good would be
attained by taking under their protection the little creatures which
are the authors of this excretion. From this time the ants would begin
to abandon their sanguinary propensities and manifest some regard for
the aphides. The latter, in return, perceiving the former’s friendly
disposition, would cease to fear them, and learn to cater to their
wants. Thus would be developed, in time, those amicable relations which
subsist between the two great, yet widely differentiated, families.
MILCH-COWS OF THE ANTS.
While much has been written upon the social relations subsisting
between ants and aphides, yet the subject never grows uninteresting or
threadbare. New facts are brought to light as observations widen and
extend, some tending to confirm, and others to subvert old notions.
That aphides excrete a sweet, viscid, honey-like fluid, which affords
food for many species of ants, has been long known to naturalists.
Any one can convince himself of this truth if he will but put himself
to the trouble of examining the leaves or branchlets of any plant at
the proper season of the year. Scattered upon the foliage and tender
twigs thereof will be found millions of aphides, and close beside them
countless ants, that ever and anon will be seen to caress, by means of
their antennæ, the little creatures for the sweets within their bodies.
It has even been asserted that some species of ants keep aphides as
human beings do cows, but this by the many has been doubted, or deemed
imaginary.
When a young man the writer was disposed to drift with the popular
opinion in this particular, but a few facts that fell under his notice
whilst searching for carabi and other beetles that live under stones
and decayed logs, changed the bias of his mind and established in him
the idea that with one species of ant this was at least the case.
It was on an occasion while exploring a neighboring thicket for the
objects of his search, that he discovered, underneath a large flat
stone which he had raised, a nest of a small red ant, which he took
to be the _Lasius flavus_ of the books. The ground was covered all
over with pits, and divers communicating roads, and round about were
hundreds of ants, larvæ in various stages of development, pupæ and
eggs, and innumerous flocks of a white aphis, all of which were being
tenderly cared for by a large army of thoughtful nurses.
[Illustration: NEST OF LASIUS.
Neuters About Their Work.]
No sooner did the intrusion occur than the colony was a scene of
busy activity. Interested in what was before him, the writer seated
himself upon a small mound overlooking the nest, where could be clearly
observed the minutest details of ant-life. The neuters were everywhere
to be noticed, but not a single male or female ant. All the work
devolved upon the neuters. These were divided into three sets, each set
having a definite part to perform in the unexpected drama before it.
Some neuters had the exclusive charge of the mature larvæ, others of
the pupæ and very young grubs, and the rest of their aphidian herds.
But it is to those that had the care of the aphides that we shall
particularly invite attention. At the time of the disturbance, these
specialized neuters were busy milking their cows, which they did
by rubbing their long, pliant feelers against the anal nipples of
the latter, drawing therefrom, as it seemed, a drop of the coveted
fluid with each antennal stroke. No aphis was known to be visited in
this business twice in succession, but the ants would go from one to
another, and only return to the first when sufficient time had elapsed
for the replenishing of its store. So intent were they upon their task,
that several minutes must have passed before they took in the danger to
which they were exposed.
You should then have seen their anxiety, and the presence of mind they
exhibited. Conscious as of attack, and knowing the peril that beset
them, they did not flee to their underground galleries, or to the
adjoining grasses, for shelter, and thus leave their flocks to the
mercy of the invader, but they manifested the deepest concern for the
little creatures, so unable to defend themselves, that had so willingly
catered to their temporal wants. Not an ant was seen to desert its
post, but all remained on duty till the last of their protegés was
carried to safe and comfortable apartments in the ground beneath.
What clearer evidence is wanted to show the love these neuters bear the
tender objects of their care? It must be plain that man bestows not
half the attention upon his flocks than do these ants on theirs. It is
true they do not bring them food, but that they build their homes where
food, the roots of herbs and grasses, abound, there is no doubt. It
may be, too, that they are carried to their pasture-grounds, when that
necessity occurs, but this cannot with truth be said. When some would
stray, they were returned within the fold, which shows the watch these
ants do exercise.
Concluding then, this much may be averred: food, wholesome, sweet,
nutritious food, the aphides supply to ants, the neuters and the young,
but specially the young. And that they lead most happy, prosperous
lives, the ants their masters, must surely be, or looks deceive.
LIVING ARTILLERY.