[There is a good series of the queen cells of the Termite in the

British Museum, and the reader is strongly recommended to go and

examine them. Some of them are as large as cocoa-nuts. Around the

cell are a number of small holes, looking as if they had been bored

with a bradawl. Now, if the cell be carefully opened, a most curious

arrangement will be seen. Each of the little holes serves as an opening

into a passage which communicates with the interior of the cell. The

apartment, if we may so call it, which contains the queen, is only

just large enough to hold her, and there is no door or opening for her

egress. This, however, is not required, as her enormous size prevents

her from moving. Through these passages runs incessantly a stream of

worker termites, some of them carrying eggs which the queen has just

laid, and others returning to the royal chamber for a fresh supply.]

The royal chamber, if in a large hillock, is surrounded by a countless

number of others, of different sizes, shapes, and dimensions; but all

of them arched in one way or another--sometimes elliptical or oval.

These either open into each other, or communicate by passages as wide

as, and are evidently made for, the soldiers and attendants, of whom

great numbers are necessary, and always in waiting. These apartments

are joined by the magazines and nurseries. The former are chambers of

clay, and are always well filled with provisions, which, to the naked

eye, seem to consist of the raspings of wood, and plants which the

termites destroy, but are found by the microscope to be principally

the gums or inspissated juices of plants. These are thrown together in

little masses, some of which are finer than others, and resemble the

sugar about preserved fruits; others are like tears of gum, one quite

transparent, another like amber, a third brown, and a fourth quite

opaque, as we see often in parcels of ordinary gums. These magazines

are intermixed with the nurseries, which are buildings totally

different from the rest of the apartments; for these are composed

entirely of wooden materials, seemingly joined together with gums. Mr.

Smeathman calls them the nurseries because they are invariably occupied

by the eggs and young ones, which appear at first in the shape of

labourers, but white as snow. These buildings are exceedingly compact,

and divided into many very small irregular-shaped chambers, not one

of which is to be found of half an inch in width. They are placed all

round, and as near as possible to the royal apartments.

When the nest is in the infant state, the nurseries are close to the

royal chambers; but as, in process of time, the queen enlarges, it is

necessary to enlarge the chamber for her accommodation; and as she

then lays a greater number of eggs, and requires a greater number of

attendants, so it is necessary to enlarge and increase the number of

the adjacent apartments; for which purpose the small nurseries which

are first built are taken to pieces, rebuilt a little further of a size

larger, and the number of them increased at the same time. Thus they

continually enlarge their apartments, pull down, repair, or rebuild,

according to their wants, with a degree of sagacity, regularity, and

foresight, not even imitated by any other kind of animals or insects.

All these chambers, and the passages leading to and from them, being

arched, they help to support each other; and while the interior large

arches prevent them from falling into the centre, and keep the area

open, the exterior building supports them on the outside. There are,

comparatively speaking, few openings into the great area, and they,

for the most part, seem intended only to admit into the nurseries

that genial warmth which the dome collects. The interior building, or

assemblage of nurseries, chambers, &c., has a flattish top or roof,

without any perforation, which would keep the apartments below dry, in

case through accident the dome should receive any injury, and let in

water; and it is never exactly flat and uniform, because the insects

are always adding to it by building more chambers and nurseries; so

that the division or columns between the future arched apartment

resemble the pinnacles on the fronts of some old buildings, and demand

particular notice, as affording one proof that for the most part the

insects project their arches, and do not make them by excavation. The

area has also a flattish floor, which lies over the royal chamber,

but sometimes a good height above it, having nurseries and magazines

between. It is likewise waterproof, and contrived to let the water

off if it should get in, and run over by some short way into the

subterraneous passages, which run under the lowest apartments in the

hill in various directions, and are of an astonishing size, being

wider than the bore of a great cannon. One that Mr. Smeathman measured

was perfectly cylindrical, and thirteen inches in diameter. These

subterraneous passages, or galleries, are lined very thick with the

same kind of clay of which the hill is composed, and ascend the inside

of the outward shell in a spiral manner; and winding round the whole

building up to the top, intersect each other at different heights,

opening either immediately in the dome in various places, and into the

interior building, the new turrets, &c., or communicating with them by

other galleries of different diameters, either circular or oval.

From every part of these large galleries are various small covert

ways, or galleries leading to different parts of the building. Under

ground there are a great many that lead downward by sloping descents,

three and four feet perpendicular among the gravel, whence the workers

cull the finer parts, which, being kneaded up in their mouths to the

consistence of mortar, become that solid clay or stone of which their

hills and all their buildings, except their nurseries, are composed.

Other galleries again ascend, and lead out horizontally on every side,

and are carried under ground near to the surface a vast distance: for

if all the nests are destroyed within a hundred yards of a house, the

inhabitants of those which are left unmolested farther off will still

carry on their subterraneous galleries, and, invading it by sap and

mine, do great mischief to the goods and merchandise contained in it.

It seems there is a degree of necessity for the galleries under the

hills being thus large, since they are the great thoroughfares for

all the labourers and soldiers going forth or returning, whether

fetching clay, wood, water, or provisions; and they are certainly well

calculated for the purposes to which they are applied by the spiral

slope which is given them; for if they were perpendicular the labourers

would not be able to carry on their building with so much facility, as

they ascend a perpendicular with great difficulty, and the soldiers can

scarcely do it at all. It is on this account that sometimes a road like

a ledge is made on the perpendicular side of any part of the building

within their hill, which is flat on the upper surface and half an inch

wide, and ascends gradually like a staircase, or like those winding

roads which are cut on the sides of hills and mountains, that would

otherwise be inaccessible; by which and similar contrivances they

travel with great facility to every interior part.

[Illustration: _a_, A covered way and nest, on the branch of a tree, of

the _Termites arborum_. _b_, Section of the Hill-nest of the _Termites

bellicosi_, to show the interior. _c_, Hill-nest of the _Termites

bellicosi_, entire.]

This, too, is probably the cause of their building a kind of bridge

of one great arch, which answers the purpose of a flight of stairs

from the floor of the area to some opening on the side of one of the

columns that support the great arches. This contrivance must shorten

the distance exceedingly to those labourers who have the eggs to carry

from the royal chamber to some of the upper nurseries, which in some

hills would be four or five feet in the straightest line, and much more

if carried through all the winding passages leading through the inner

chambers and apartments. Mr. Smeathman found one of these bridges, half

an inch broad, a quarter of an inch thick, and ten inches long, making

the side of an elliptic arch of proportionable size; so that it is

wonderful it did not fall over or break by its own weight before they

got it joined to the side of the column above.

It was strengthened by a small arch at the bottom, and had a hollow or

groove all the length of the upper surface, either made purposely for

the inhabitants to travel over with more safety, or else, which is not

improbable, worn by frequent treading.

Turret-building White Ants.

Apparently more than one species smaller than the preceding, such

as the _Termes mordax_ and _T. atrox_ of Smeathman, construct nests

of a very different form, the figures of which resemble a pillar,

with a large mushroom for a capital. These turrets are composed of

well-tempered black earth, and stand nearly three feet high. The

conical mushroom-shaped roof is composed of the same material, and

the brims hang over the column, being three or four inches wider than

its perpendicular sides. Most of them, says Smeathman, resemble in

shape the body of a round windmill, but some of the roofs have little

elevation in the middle. When one of these turrets is completed, the

insects do not afterwards enlarge or alter it; but if it be found too

small for them, they lay the foundation of another at a few inches'

distance. They sometimes, but not often, begin the second before the

first is finished, and a third before they have completed the second.

Five or six of these singular turrets in a group may be seen in the

thick woods at the foot of a tree. They are so very strongly built,

that in case of violence, they will sooner tear up the gravel and

solid heart of their foundation than break in the middle. When any of

them happen to be thus thrown down, the insects do not abandon them;

but, using their overturned column as a basis, they run up another

perpendicularly from it to the usual height, fastening the under part

at the same time to the ground, to render it the more secure.

The interior of a turret is pretty equally divided into innumerable

cells, irregular in shape, but usually more or less angular, generally

quadrangular or pentagonal, though the angles are not well defined.

Each shell has at least two entrances; but there are no galleries,

arches, nor wooden nurseries, as in the nests of the warrior (_T.

bellicosus_). The two species which build turret nests are very

different in size, and the dimensions of the nests differ in proportion.

[Illustration: Turret Nests of White Ants. One nest is represented cut

through, with the upper part lying on the ground.]

The White Ants of Trees.

Latreille's species of white ant (_Termes lucifugus_, Rossi), formerly

mentioned as found in the south of Europe, appear to have more the

habits of the jet-ant, described page 301, than their congeners of the

tropics. They live in the interior of the trunks of trees, the wood

of which they eat, and form their habitations of the galleries which

they thus excavate. M. Latreille says they appear to be furnished with

an acid for the purpose of softening the wood, the odour of which

is exceedingly pungent. They prefer the part of the wood nearest to

the bark, which they are careful not to injure, as it affords them

protection. All the walls of their galleries are moistened with small

globules of a gelatinous substance, similar to gum Arabic. They are

chiefly to be found in the trunks of oak and pine trees, and are very

numerous.[DP]

Another of the species (_Termes arborum_), described by Smeathman,

builds a nest on the exterior of trees, altogether different from any

of the preceding. These are of a spherical or oval shape, occupying

the arm or branch of a tree sometimes from seventy to eighty feet

from the ground, and as large, in a few instances, as a sugar-cask.

The composition used for a building material is apparently similar

to that used by the warriors for constructing their nurseries, being

the gnawings of wood in very small particles, kneaded into a paste

with some species of cement or glue, procured, as Smeathman supposes,

partly from gummiferous trees, and partly from themselves; but it is

more probable, we think, that it is wholly secreted, like the wax of

bees, by the insects themselves. With this cement, whatever may be its

composition, they construct their cells, in which there is nothing

very wonderful except their great numbers. They are very firmly built,

and so strongly attached to the trees, that they will resist the most

violent tornado. It is impossible, indeed, to detach them, except by

cutting them in pieces, or sawing off the branch, which is frequently

done to procure the insects for young turkeys. (See engraving, p. 324,

for a figure of this nest.)

This species very often, instead of selecting the bough of a tree,

builds in the roof or wall of a house, and unless observed in time,

and expelled, occasions considerable damage. It is easier, in fact,

to shut one's door against a fox or a thief, than to exclude such

insidious enemies, whose aversion to light renders it difficult to

trace them even when they are numerous.

[There are also termites in Europe, and the city of La Rochelle has

suffered terribly from them. They eat the trees in the gardens, and

not a stake can be driven into the ground, or even a plank left for

twenty-four hours, without being attacked. They also enter the houses

and utterly ruin them by eating every bit of timber that is used in

them. In one instance, where a room had been repaired, the stalactitic

galleries of the termites showed themselves the very day after the

workmen had left the room.

They invaded the prefecture, and did exceeding damage, one of their

feats of voracity being so extraordinary as to deserve mention. The

archives of the department were left in boxes, and privately inspected.

One day, when a paper was needed, the whole of the documents fell to

pieces, and were metamorphosed as if by magic into a heap of clay. The

termites had got into the boxes by boring through the wainscot of the

room, and had then penetrated among the papers. They consumed every

particle of them except the uppermost sheet and the edges, supplying

their place with clay. The consequence was, that although the heap of

documents seemed to be correct, there was nothing but a mass of clay

galleries and a single sheet of paper at the top.

So voracious are they, that even a piece of paper wrapped round a

bottle was eaten, the termites building a gallery of clay in order to

reach it under cover.]

If we reflect on the prodigious numbers of those insects, and their

power and rapidity of destroying, we cannot but admire the wisdom

of Providence in creating so indefatigable and useful an agent

in countries where the decay of vegetable substances is rapid in

proportion to the heat of the climate. We have already remarked that

they always prefer decaying or dead timber; and it is indeed a very

general law among insects which feed on wood to prefer what is

unsound; the same principle holds with respect to fungi, lichens, and

other parasitical plants.

All the species of Termites are not social; but the solitary ones do

not, like their congeners, distinguish themselves in architecture. In

other respects, their habits are more similar; for they destroy almost

every substance, animal and vegetable. The most common of the solitary

species must be familiar to all our readers by the name of wood-louse

(_Termes pulsatorium_, Linn.; _Atropos lignarius_, Leach)--one of

the insects which produces the ticking superstitiously termed the

_death-watch_. It is not so large as the common wood-louse, but whiter

and more slender, having a red mouth and yellow eyes. It lives in old

books, the paper on walls, collections of insects and dried plants,

and is extremely agile in its movements, darting, by jerks, into

dark corners for the purpose of concealment. It does not like to run

straight forward without resting every half-second, as if to listen

or look about for its pursuer, and at such resting times it is easily

taken. The ticking noise is made by the insect beating against the

wood with its head, and it is supposed by some to be peculiar to the

female, and to be connected with the laying of her eggs. M. Latreille,

however, thinks that the wood-louse is only the grub of the _Psocus

abdominalis_, in which case it could not lay eggs; but this opinion is

somewhat questionable. Another death-watch is a small beetle (_Anobium

tesselatum_).

_CHAPTER XVII._

STRUCTURES OF SILK SPUN BY CATERPILLARS, INCLUDING THE SILK-WORM.

"Millions of spinning-worms,

That in their green shops weave the smooth-hair'd silk."

Milton's _Comus_.

All the caterpillars of butterflies, moths, and, in general, of insects

with four wings, are capable of spinning silk; of various degrees of

fineness and strength, and differing in colour, but usually white,

yellow, brown, black, or grey. This is not only of advantage in

constructing nests for themselves, and particularly for their pupæ,

as we have so frequently exemplified in the preceding pages, but it

enables them, the instant they are excluded from the egg, to protect

themselves from innumerable accidents, as well as from enemies. If a

caterpillar, for instance, be exposed to a gust of wind, and blown off

from its native tree, it lets itself gently down, and breaks its fall,

by immediately spinning a cable of silk, along which, also, it can

reascend to its former station when the danger is over. In the same way

it frequently disappoints a bird that has marked it out for prey, by

dropping hurriedly down from a branch, suspended to its never-failing

delicate cord. The leaf-rollers, formerly described, have the advantage

of other caterpillars in such cases, by being able to move as quickly

backwards as forwards; so that when a bird puts in its bill at one

end of the roll, the insect makes a ready exit at the other, and

drops along its thread as low as it judges convenient. We have seen

caterpillars drop in this way from one to six feet or more; and by

means of their cable, which they are careful not to break, they climb

back with great expedition to their former place.

The structure of their legs is well adapted for climbing up their

singular rope--the six fore-legs being furnished with a curved claw;

while the pro-legs (as they have been termed) are no less fitted for

holding them firm to the branch when they have regained it, being

constructed on the principle of forming a vacuum, like the leather

sucker with which boys lift and drag stones. The foot of the common

fly has a similar sucker, by which it is enabled to walk on glass, and

otherwise support itself against gravity. The different forms of the

leg and pro-leg of a spinning caterpillar are represented in the figure.

[Illustration: Leg and Pro-leg of a Caterpillar, greatly magnified.]

In order to understand the nature of the apparatus by which a

caterpillar spins its silk, it is to be recollected that its whole

interior structure differs from that of warm-blooded animals. It has,

properly speaking, no heart, though a long tubular _dorsal vessel_,

which runs along the back, and pulsates from twenty to one hundred

times per minute, has been called so by Malpighi and others, but

neither Lyonnet nor Cuvier could detect any vessel issuing from it, and

consequently the fluid which is analogous to blood has no circulation.

It differs also from the higher orders of animals in having no brain,

the nerves running along the body being only united by little knobs,

called ganglions. Another circumstance is, that it has no lungs,

and does not breathe by the mouth, but by air-holes, or spiracles,

eighteen in number, situated along the sides, in the middle of the

rings, as may be seen in the following figure from Lyonnet.

[Illustration: Caterpillar of the Goat Moth (_Cossus ligniperda_).]

These spiracles communicate on each side with tubes, that have been

called the wind-pipes (_tracheæ_). The spinning apparatus is placed

near the mouth, and is connected with the silk-bags, which are long,

slender, floating vessels, containing a liquid gum. The bags are closed

at their lower extremity, become wider towards the middle, and more

slender towards the head, where they unite to form the spinning-tube,

or spinneret. The bags being in most cases longer than the body of the

caterpillar, necessarily lie in a convoluted state, like the intestines

of quadrupeds. The capacity, or rather the length, of the silk-bags

is in proportion to the quantity of silk required for spinning; the

_Cossus ligniperda_, for example, from living in the wood of trees

spins little, having a bag only one-fourth the length of that of the

silk-worm, though the caterpillar is at least twice the dimensions of

the latter. The following figure, taken from the admirable treatise

of Lyonnet on the anatomy of the _Cossus_, will render these several

organs more easily understood than any description.

The spinneret itself was supposed by Réaumur to have two outlets for

the silk; but Lyonnet, upon minute dissection, found that the two tubes

united into one before their termination; and he also assured himself

that it was composed of alternate slips of horny and membranaceous

substance,--the one for pressing the thread into a small diameter,

and the other for enlarging it at the insect's pleasure. It is cut at

the end somewhat like a writing-pen, though with less of a slope, and

is admirably fitted for being applied to objects to which it may be

required to attach silk. The following are magnified figures of the

spinneret of the _Cossus_, from Lyonnet.

[Illustration: Interior Structure of the Cossus.--A, silk bags; B, silk

tube, through which the viscid matter, of which the silk threads are

formed, is forced by a peristaltic motion; C, stomach; D D, intestines,

with the coil of bile vessels.]

[Illustration: Side-view of the Silk-tube.]

[Illustration: Section of the Silk-tube, magnified 22,000 times.]

[Illustration: Labium, or lower lip of Cossus.--_a_, Silk-tube.]

"You may sometimes have seen," says the Abbé de la Pluche, "in the

work-rooms of goldsmiths or gold wire-drawers, certain iron plates,

pierced with holes of different calibres, through which they draw gold

and silver wire, in order to render it finer. The silk-worm has under

her mouth such a kind of instrument, perforated with a pair of holes

[united into one on the outside[DQ],] through which she draws two drops

of the gum that fills her two bags. These instruments are like a pair

of distaffs for spinning the gum into a silken thread. She fixes the

first drop of gum that issues where she pleases, and then draws back

her head, or lets herself fall, while the gum, continuing to flow, is

drawn out and lengthened into a double stream. Upon being exposed to

the air, it immediately loses its fluidity, becomes dry, and acquires

consistence and strength. She is never deceived in adjusting the

dimensions of the [united] apertures, or in calculating the proper

thickness of the thread, but invariably makes the strength of it

proportionable to the weight of her body.

"It would be a very curious thing to know how the gum which composes

the silk is separated and drawn off from the other juices that nourish

the animal. It must be accomplished like the secretions formed by

glands in the human body. I am therefore persuaded that the gum-bags of

the silk-worm are furnished with a set of minute glands, which being

impregnated with gum, afford a free passage to all the juices of the

mulberry-leaf corresponding with this glutinous matter, while they

exclude every fluid of a different quality."[DR] When confined in an

open glass vessel, the goat-moth caterpillar will effect its escape by

constructing a curious silken ladder, as represented by Roesel.

Caterpillars, as they increase in size, cast their skins as lobsters

do their shells, and emerge into renewed activity under an enlarged

covering. Previous to this change, when the skin begins to gird and

pinch them, they may be observed to become languid, and indifferent to

their food, and at length they cease to eat, and await the sloughing of

their skin. It is now that the faculty of spinning silk seems to be of

great advantage to them; for, being rendered inactive and helpless by

the tightening of the old skin around their expanding body, they might

be swept away by the first puff of wind, and made prey of by ground

beetles or other carnivorous prowlers. To guard against such accidents,

as soon as they feel that they can swallow no more food, from being

half choked by the old skin, they take care to secure themselves from

danger by moorings of silk spun upon the leaf or the branch where they

may be reposing. The caterpillar of the white satin-moth (_Leucoma

salicis_, Stephens) in this way draws together with silk one or two

leaves, similar to the leaf-rollers (_Tortricidæ_), though it always

feeds openly without any covering. The caterpillar of the puss-moth

again, which, in its third skin, is large and heavy, spins a thick web

on the upper surface of a leaf, to which it adheres till the change is

effected.

The most important operation, however, of silk-spinning is performed

before the caterpillar is transformed into a chrysalis, and is

most remarkable in the caterpillars of moths and other four-winged

flies, with the exception of those of butterflies; for though these

exhibit, perhaps, greater ingenuity, they seldom spin more than a

few threads to secure the chrysalis from falling, whereas the others

spin for it a complete envelope or shroud. We have already seen, in

the preceding pages, several striking instances of this operation,

when, probably for the purpose of husbanding a scanty supply of silk,

extraneous substances are worked into the texture. In the case of other

caterpillars, silk is the only material employed.

Of this the cocoon of the silk-worm is the most prominent example, in

consequence of its importance in our manufactures and commerce, and on

that account will demand from us somewhat minute details, though it

would require volumes to incorporate all the information which has been

published on the subject.

Silk-Worm.

The silk-worm, like most other caterpillars, changes its skin four

times during its growth. The intervals at which the four moultings

follow each other depend much on climate or temperature, as well as

on the quality and quantity of food. It is thence found, that if they

are exposed to a high temperature, say from 81° to 100° Fahrenheit,

the moultings will be hastened; and only five days will be consumed in

moulting the third or fourth time, whilst those worms that have not

been hastened take seven or eight days.[DS]

The period of the moultings is also influenced by the temperature in

which the eggs have been kept during the winter. When the heat of the

apartment has been regulated, the first moulting takes place on the

fourth or fifth day after hatching, the second begins on the eighth

day, the third takes up the thirteenth and fourteenth days, and the

last occurs on the twenty-second and twenty-third days. The fifth age,

in such cases, lasts ten days, at the end of which, or thirty-two days

after hatching, the caterpillars attain their full growth, and ought to

be three inches in length; but if they have not been properly fed, they

will not be so long.

With the age of the caterpillar, its appetite increases, and is at its

maximum after the fourth moulting, when it also attains its greatest

size. The silk gum is then elaborated in the reservoirs, while the

caterpillar ceases to eat, and soon diminishes again in size and

weight. This usually requires a period of nine or ten days, commencing

from the fourth moulting, after which it begins to spin its shroud of

silk. In this operation it proceeds with the greatest caution, looking

carefully for a spot in which it may be most secure from interruption.

"We usually," says the Abbé de la Pluche, "give it some little stalks

of broom, heath, or a piece of paper rolled up, into which it retires,

and begins to move its head to different places, in order to fasten its

thread on every side. All this work, though it looks to a bystander

like confusion, is not without design. The caterpillar neither arranges

its threads nor disposes one over another, but contents itself with

distending a sort of cotton or floss to keep off the rain; for Nature

having ordained silk-worms to work under trees, they never change their

method even when they are reared in our houses.

"When my curiosity led me to know how they spun and placed their

beautiful silk, I took one of them, and frequently removed the floss

with which it first attempted to make itself a covering; and as by

this means I weakened it exceedingly, when it at last became tired

of beginning anew, it fastened its threads on the first thing it

encountered, and began to spin very regularly in my presence, bending

its head up and down, and crossing to every side. It soon confined

its movements to a very contracted space, and, by degrees, entirely

surrounded itself with silk; and the remainder of its operations became

invisible, though these may be understood from examining the work

after it is finished. In order to complete the structure, it must draw

out of the gum-bag a more delicate silk, and then with a stronger gum

bind all the inner threads over one another.

"Here, then, are three coverings entirely different, which afford a

succession of shelter. The outer loose silk, or floss, is for keeping

off the rain; the fine silk in the middle prevents the wind from

causing injury; and the glued silk, which composes the tapestry of

the chamber where the insect lodges, repels both air and water, and

prevents the intrusion of cold.

"After building her cocoon, she divests herself of her fourth skin, and

is transformed into a chrysalis, and subsequently into a moth (_Bombyx

mori_), when, without saw or centre-bit, she makes her way through the

shell, the silk, and the floss; for the Being who teaches her how to

build herself a place of rest, where the delicate limbs of the moth may

be formed without interruption, instructs her likewise how to open a

passage for escape.

"The cocoon is like a pigeon's egg, and more pointed at one end

than the other; and it is remarkable that the caterpillar does not

interweave its silk towards the pointed end, nor apply its glue there

as it does in every other part,[DT] by bending itself all around with

great pliantness and agility: what is more, she never fails, when her

labour is finished, to fix her head opposite to the pointed extremity.

The reason of her taking this position is, that she has purposely

left this part less strongly cemented, and less exactly closed. She

is instinctively conscious that this is to be the passage for the

perfect insect which she carries in her bowels, and has therefore the

additional precaution never to place this pointed extremity against any

substance that might obstruct the moth at the period of its egress.

"When the caterpillar has exhausted herself to furnish the labour and

materials of the three coverings, she loses the form of a worm; her

spoils drop all around the chrysalis; first throwing off the skin,

with the head and jaws attached to it, and the new skin hardening

into a sort of leathery consistence. Its nourishment is already in its

stomach, and consists of a yellowish mucus, but gradually the rudiments

of the moth unfold themselves,--the wings, the antennæ, and the legs

becoming solid. In about a fortnight or three weeks, a slight swelling

in the chrysalis may be remarked, which at length produces a rupture in

the membrane that covers it, and by repeated efforts the moth bursts

through the leathery envelope into the chamber of the cocoon.

"The moth then extends her antennæ, together with her head and feet,

towards the point of the cone, which not being thickly closed up in

that part gradually yields to her efforts; she enlarges the opening,

and at last comes forth, leaving at the bottom of the cone the ruins of

its former state--namely, the head and entire skin of the caterpillar,

which bear some resemblance to a heap of foul linen."[DU]

Réaumur was of opinion that the moth makes use of its eyes as a file,

in order to effect its passage through the silk; while Malpighi, Peck,

and others, believe that it is assisted by an acid which it discharges

in order to dissolve the gum that holds the fibres of the silk together

(see p. 338). Mr. Swayne denies that the threads are broken at all,

either by filing or solution; for he succeeded in unwinding a whole

cocoon from which the moth had escaped. The soiling of the cocoon by a

fluid, however, we may remark, is no proof of the acid; for all moths

and butterflies discharge a fluid when they assume wings, whether they

be inclosed in a cocoon or not; but it gives no little plausibility to

the opinion, that "the end of the cocoon is observed to be wetted for

an hour, and sometimes several hours, before the moth makes its way

out."[DV] Other insects employ different contrivances for escape, as we

have already seen, and shall still further exemplify.

It is the middle portion of the cocoon, after removing the floss or

loose silk on the exterior, which is used in our manufactures; and the

first preparation is to throw the cocoons into warm water, and to stir

them about with twigs, to dissolve any slight gummy adhesions which may

have occurred when the caterpillar was spinning. The threads of several

cones, according to the strength of the silk wanted, are then taken and

wound off upon a reel. The refuse, consisting of what we may call the

tops and bottoms of the cones, are not wound, but carded, like wool or

cotton, in order to form coarser fabrics. We learn from the fact of the

cocoons being generally unwound without breaking the thread, that the

insect spins the whole without interruption. It is popularly supposed,

however, that if it be disturbed during the operation by any sort of

noise, it will take alarm, and break its thread; but Latreille says

this is a vulgar error.[DW]

The length of the unbroken thread in a cocoon varies from six hundred

to a thousand feet; and as it is all spun double by the insect, it

will amount to nearly two thousand feet of silk, the whole of which

does not weigh above three grains and a half; five pounds of silk from

ten thousand cocoons is considerably above the usual average. When

we consider, therefore, the enormous quantity of silk which is used

at present, the number of worms employed in producing it will almost

exceed our comprehension. The manufacture of the silk, indeed, gives

employment, and furnishes subsistence, to several millions of human

beings; and we may venture to say, that there is scarcely an individual

in the civilized world who has not some article made of silk in his

possession.

In ancient times, the manufacture of silk was confined to the East

Indies and China, where the insects that produce it are indigenous. It

was thence brought to Europe in small quantities, and in early times

sold at so extravagant a price, that it was deemed too expensive even

for royalty. The Emperor Aurelian assigned the expense as a reason for

refusing his empress a robe of silk; and our own James I., before his

accession to the crown of England, had to borrow of the Earl of Mar a

pair of silk stockings to appear in before the English ambassador,

a circumstance which probably led him to promote the cultivation of

silk in England.[DX] The Roman authors were altogether ignorant of

its origin,--some supposing it to be grown on trees as hair grows

on animals,--others that it was produced by a shell-fish similar to

the mussel, which is known to throw out threads for the purpose of

attaching itself to rocks,--others that it was the entrails of a sort

of spider, which was fed for four years with paste, and then with the

leaves of the green willow, till it burst with fat,--and others that it

was the produce of a worm which built nests of clay and collected wax.

The insect was at length spread into Persia; and eggs were afterwards,

at the instance of the Emperor Justinian, concealed in hollow canes by

two monks, and conveyed to the Isle of Cos. This emperor, in the sixth

century, caused them to be introduced into Constantinople, and made an

object of public utility. They were thence successively cultivated in

Greece, in Arabia, in Spain, in Italy, in France, and in all places

where any hope could be indulged of their succeeding. In America the

culture of the silk-worm was introduced into Virginia in the time of

James I., who himself composed a book of instructions on the subject,

and caused mulberry-trees and silk-worms' eggs to be sent to the

colony. In Georgia, also, lands were granted on condition of planting

one hundred white mulberry-trees on every ten acres of cleared land.[DY]

The growth of the silk-worm has also been tried, but with no great

success, in this country. Evelyn computed that one mulberry-tree would

feed as many silk-worms annually as would produce seven pounds of

silk. "According to that estimate," says Barham,[DZ] "the two thousand

trees already planted in Chelsea Park (which take up one-third of

it) will make 14,000 lbs. weight of silk; to be commonly worth but

twenty shillings a pound, those trees must make 14,000_l._ per annum."

During the last century, some French refugees in the south of Ireland

made considerable plantations of the mulberry, and had begun the

cultivation of silk with every appearance of success; but since their

removal the trees have been cut down.[EA] In the vicinity of London,

also, a considerable plantation of mulberry-trees was purchased by the

British, Irish, and Colonial Silk Company in 1825; but we have not

learned whether this Company have any active measures now in operation.

The manufacture of silk was introduced into this country in 1718,

at Derby, by Mr. John Lombe, who travelled into Italy to obtain the

requisite information; but so jealous were the Italians of this, that

according to some statements which have obtained belief, he fell a

victim to their revenge, having been poisoned at the early age of

twenty-nine.[EB]

There are not only several varieties of the common silk-worm (_Bombyx

mori_), but other species of caterpillars, which spin silk capable of

being manufactured, though not of so good qualities as the common silk.

None of our European insects, however, seem to be well fitted for the

purpose, though it has been proposed by Fabricius and others to try

the crimson under-wing (_Catocala sponsa_, Schrank), &c. M. Latreille

quotes from the 'Recreations of Natural History,' by Wilhelm, the

statement that the cocoons of the emperor-moth (_Saturnia pavonia_)

had been successfully tried in Germany, by M. Wentzel Hegeer de

Berchtoldsdorf, under an imperial patent.

[Illustration: Cocoons of the Emperor-moth, cut open to show their

structure.]

Emperor-Moth.

The emperor-moth, indeed, is no less worthy of our attention with

respect to the ingenuity of its architecture than the beauty of

its colours, and has consequently attracted the attention of every

Entomologist. The caterpillar feeds on fruit-trees and on the willow,

and spins a cocoon, in the form of a Florence flask, of strong silk,

so thickly woven that it appears almost like damask or leather. It

differs from most other cocoons in not being closed at the upper or

smaller end, which terminates in a narrow circular aperture, formed

by the convergence of little bundles of silk, gummed together, and

almost as elastic as whalebone. In consequence of all these terminating

in needle-shaped points, the entrance of depredators is guarded

against, upon the principle which prevents the escape of a mouse from

a wire trap. The insect, however, not contented with this protection,

constructs another in form of a canopy or dome, within the external

aperture, so as effectually to shield the chrysalis from danger.

We have formerly remarked (page 210) that the caterpillar of the

_Ægeria asiliformis_ of Stephens in a similar way did not appear to be

contented with a covering of thin wood, without an additional bonnet of

brown wax. The cocoon of the emperor-moth, though thus in some measure

impenetrable from without, is readily opened from within; and when the

moth issues from its pupa case, it easily makes its way out without

either the acid or eye-files ascribed to the silk-worm. The elastic

silk gives way upon being pushed from within, and when the insect is

fairly out, it shuts again of its own accord, like a door with spring

hinges,--a circumstance which at first puzzled Roesel not a little when

he saw a fine large moth in his box, and the cocoon apparently in the

same state as when he had put it there. Another naturalist conjectures

that the converging threads are intended to compress the body of the

moth as it emerges, in order to force the fluids into the nervures

of the wings; for when he took the chrysalis previously out of the

cocoon, the wings of the moth never expanded properly.[EC] Had he been

much conversant with breeding insects, he would rather, we think,

have imputed this to some injury which the chrysalis had received.

We have witnessed the shrivelling of the wings which he alludes to,

in many instances, and not unfrequently in butterflies which spin no

cocoon. The shrivelling, indeed, frequently arises from the want of

a sufficient supply of food to the caterpillar in its last stage,

occasioning a deficiency in the fluids.

The elasticity of the cocoon is not peculiar to the emperor-moth. A

much smaller insect, the green cream-border-moth (_Tortrix chlorana_)

before mentioned (page 190), for its ingenuity in bundling up the

expanding leaves of the willow, also spins an elastic shroud for its

chrysalis, of the singular shape of a boat with the keel uppermost.

Like the caterpillar of _Pyralis strigulalis_ (page 217), whose

building, though of different materials, is exactly of the same form,

its first spins two approximating walls of whitish silk, of the form

required, and when these are completed, it draws them forcibly together

with elastic threads, so placed as to retain them closely shut. The

passage of the moth out of this cocoon might have struck Roesel as

still more marvellous than that of his emperor, in which there was at

least a small opening; while in the boat cocoon there is none. We have

now before us two of these, which we watched the caterpillars through

the process of building, in the summer of 1828, and from one only a

moth issued--the other, as often happens, having died in the chrysalis.

But what is most remarkable, it is impossible by the naked eye to tell

which of these two has been opened by the moth, so neatly has the

joining been finished. (J. R.)

Some species of moths spin a very slight silken tissue for their

cocoons, being apparently intended more to retain them from falling

than to afford protection from other accidents. The gipsy-moth

(_Hypogymna dispar_), rare in most parts of Britain, is one of these.

It selects for its retreat a crack in the bark of the tree upon which

it feeds, and over this spins only a few straggling threads. We found

last summer (1829), in the hole of an elm-tree in the Park at Brussels,

a group of half a dozen of these, that did not seem to have spun any

covering at all, but trusted to a curtain of moss (_Hypna_) which

margined the entrance. (J. R.) In a species nearly allied to this,

the yellow-tussock (_Dasychira pudibunda_, Stephens), the cocoon, one

of which we have now before us, is of a pretty close texture, and

interwoven with the long hairs of the caterpillar itself (see figure

_b_, page 17), which it plucks out piecemeal during the process of

building,--as is also done by the vapourer (_Orgyia antiqua_, Hubner),

and many others.

[Illustration: Cocoon of Arctia villica.]

[Illustration: Net-work cocoon.]

These are additional instances of the remarks we formerly made, that

caterpillars which spin a slight web are transformed into perfect

insects in a much shorter period than those which spin more substantial

ones. Thus the cream-spot tiger (_Arctia villica_, Stephens) lies in

chrysalis only three weeks, and therefore does not require a strong

web. It is figured above, along with another, which is still slighter,

though more ingeniously woven, being regularly meshed like net-work.

A very prettily-netted cocoon is constructed by the grub of a very

small grey weevil (_Hypera rumicis_), which is not uncommon in July,

on the seed spikes of docks (_Rumices_). This cocoon is globular, and

not larger than a garden pea, though it appears to be very large in

proportion to the pupa of the insect, reminding us not a little of the

carved ivory balls from China. The meshes of the net-work are also

large, but the materials are strong and of a waxy consistence. Upon

remarking that no netting was ever spun over the part of the plant

to which the cocoon was attached, we endeavoured to make them spin

cocoons perfectly globular by detaching them when nearly finished; but

though we tried four or five in this way, we could not make them add a

single mesh after removal, all of them making their escape through the

opening, and refusing to re-enter in order to complete their structure.

(J. R.)

The silk, if it may be so termed, spun by many species of larvæ is

of a still stronger texture than the waxy silk of the little weevil

just mentioned. We recently met with a remarkable instance of this at

Lee, in the cocoons of one of the larger ichneumons (_Ophion Vinulæ_?

Stephens), inclosed in that of a puss-moth (_Cerura Vinula_)--itself

remarkable for being composed of sand as well as wood, the fibres of

which had been scooped out of the underground cross-bar of an old

paling, to which it was attached. But the most singular portion of

this was the junction of the outer wall with the edges of the hollow

thus scooped out, which was formed of fibres of wood placed across

the fibres of the bar nearly at right angles, and strongly cemented

together, as if to form a secure foundation for the building.

In this nest were formed, surreptitiously introduced into the original

building, five empty cells of a black colour, about an inch long, and a

sixth of an inch in diameter; nearly cylindrical in form, but somewhat

flattened; vertical and parallel to one another, though slightly curved

on the inner side. The cells are composed of strong and somewhat

coarse fibres, more like the carbonized rootlets of a tree than silk,

and resembling in texture a piece of coarse milled cloth or felt, such

as is used for the bases of plated hats. It is worthy of remark, that

all these cells opened towards one end, as if the caterpillars which

constructed them had been aware that the wall of the puss-moth, in

which the flies would have to make a breach, was very hard, and would

require their united efforts to effect an escape. The importance of

such a precaution will appear more strikingly, when we compare it with

the instance formerly mentioned (page 215), in which only one ichneumon

had been able to force its way out. (J. R.)

[Illustration: Nest of Puss-moth, inclosing five cocoons of an

Ichneumon. Natural size.]

It appears indispensable to some grubs to be confined within a certain

space in order to construct their cocoons. We saw this well exemplified

in the instance of a grub of one of the mason-bees (_Osmia bicornis_),

which we took from its nest, and put into a box with the pollen paste

which the mother bee had provided for its subsistence. (See pages 45,

46.) When it had completed its growth, it began to spin, but in a

very awkward manner-attaching threads, as if at random, to the bits

of pollen which remained undevoured, and afterwards tumbling about to

another part of the box, as if dissatisfied with what it had done. It

sometimes persevered to spin in one place till it had formed a little

vaulted wall; but it abandoned at the least three or four of these in

order to begin others, till at length, as if compelled by the extreme

urgency of the stimulus of its approaching change, it completed a

shell of shining brown silk, woven into a close texture. Had the grub

remained within the narrow clay cell built for it by the mother bee,

it would, in all probability, not have thus exhausted itself in vain

efforts at building, which were likely to prevent it from ever arriving

at the perfect state--a circumstance which often happens in the

artificial breeding of insects. This bee, however, made its appearance

the following spring. (J. R.)

Besides silk, the cocoons of many insects are composed of other animal

secretions, intended to strengthen or otherwise perfect their texture.

We have already seen that some caterpillars pluck off their own hair

to interweave amongst their silk; there are others which produce

a peculiar substance for the same purpose. The lackey caterpillar

(_Clisiocampa neustria_, Curtis) in this manner lines its cocoon with

pellets of a downy substance, resembling little tufts of the flowers

of sulphur. The small egger, again (_Eriogaster lanestris_, Germar),

can scarcely be said to employ silk at all,--the cocoon being of a

uniform texture, looking, at first sight, like dingy Paris plaster, or

the shell of a pheasant's egg; but upon being broken, and inspected

narrowly, a few threads of silk may be seen interspersed through the

whole. In size it is not larger than the egg of the gold-crested

wren. It has been considered by Brahm a puzzling circumstance, that

this cocoon is usually perforated with one or two little holes, as if

made by a pin from without; and Kirby and Spence tell us that their

use has not been ascertained.[ED] May they not be left as air-holes

for the included chrysalis, as the close texture of the cocoon might,

without this provision, prove fatal to the animal? Yet, on comparing

one of these with a similar cocoon of the large egger-moth (_Lasiocampa

quercus_), we find no air-holes in the latter, as we might have been

led to expect from the closeness of its texture. We found a cocoon of

a saw-fly (_Trichiosoma_), about the same size as that of the egger,

attached to a hawthorn-twig, in a hedge at New Cross, Deptford, but of

a leathery texture, and, externally, exactly the colour of the bark of

the tree. During the summer of 1830 we found a considerable number of

the same cocoons. These were all without air-holes. The egger, we may

remark, unlike the dock-weevil or the bee-grub just mentioned, can work

her cocoon without any point of attachment. We had a colony of these

caterpillars in the summer of 1825, brought from Epping Forest, and saw

several of them work their cocoons, and we could not but admire the

dexterity with which they avoided filling up the little pin-holes. The

supply of their building material was evidently measured out to them

in the exact quantity required; for when we broke down a portion of

their wall, by way of experiment, they did not make it above half the

thickness of the previous portion, though they plainly preferred having

a thin wall to leaving the breach unclosed. (J. R.)

Several species of caterpillars, that spin only silk, are social, like

some of those we formerly mentioned, which unite to form a common

tent of leaves (see pages 351, 352, &c.). The most common instance

of this is in the caterpillars which feed on the nettle--the small

tortoise-shell (_Vanessa urticæ_), and the peacock's eye (_V. I._).

Colonies of these may be seen, after midsummer, on almost every clump

of nettles, inhabiting a thin web of an irregular oval shape, from

which they issue out to feed on the leaves, always returning when

their appetite is satisfied, to assist their companions in extending

their premises. Other examples, still more conspicuous from being seen

on fruit-trees and in hedges, occur in the caterpillars of the small

ermine-moth (_Yponomeuta padella_), and of the lackey (_Clisiocampa

neustria_), which in some years are but too abundant, though in others

they are seldom met with. In the summer of 1826, every hedge and

fruit-tree around London swarmed with colonies of the ermine, though

it has not since been plentiful; and in the same way, during the

summer of 1829, the lackeys were to be seen everywhere. We mention

this irregularity of appearance that our readers may not disappoint

themselves by looking for what is not always to be found. It is

probable that in 1830 the lackeys will be few, for, notwithstanding the

myriads of caterpillars last summer, we saw only a single moth of this

species, and out of a number of chrysalides which a young friend had in

his nurse-boxes, not one moth was bred.

The small ermine does not, besides, feed so indiscriminately as many

others, but when the bird-cherry (_Prunus padus_), its peculiar

food, is not to be had, it will put up with blackthorn, plum-tree,

hawthorn, and almost any sort of orchard fruit-tree. With respect to

such caterpillars as feed on different plants, Réaumur and De Geer

make the singular remark, that in most cases they would only eat the

sort of plant upon which they were originally hatched.[EE] We verified

this, in the case of the caterpillar in question, upon two different

nests which we took, in 1806, from the bird-cherry at Crawfordland,

in Ayrshire. Upon bringing these to Kilmarnock, we could not readily

supply them with the leaves of this tree; and having then only a slight

acquaintance with the habits of insects, and imagining they would eat

any sort of leaf, we tried them with almost everything green in the

vicinity of the town; but they refused to touch any which we offered

them. After they had fasted several days, we at length procured some

fresh branches of the bird-cherry, with which they gorged themselves so

that most of them died. Last summer (1829) we again tried a colony of

these caterpillars, found on a seedling plum-tree at Lee, in Kent, with

blackthorn, hawthorn, and many other leaves, and even with those of the

bird-cherry; but they would touch nothing except the seedling plum,

refusing the grafted varieties. (J. R.)

A circumstance not a little remarkable in so very nice a feeder is,

that in some cases the mother moth will deposit her eggs upon trees

not of indigenous growth, and not even of the same genus with her

usual favourites. Thus, in 1825, the cherry-apple, or Siberian crab

(_Pyrus prunifolia_, Willdenow), so commonly grown in the suburbs of

London, swarmed with them. On a single tree at Islington we counted

above twenty nests, each of which would contain from fifty to a hundred

caterpillars; and though these do not grow thicker than a crow-quill,

so many of them scarcely left a leaf undevoured, and, of course, the

fruit, which showed abundantly in spring, never came to maturity. The

summer following they were still more abundant on the hawthorn hedges,

particularly near the Thames, by Battersea and Richmond. Since then we

have only seen them sparingly; and last summer we could only find the

single nest upon which we tried the preceding experiment. (J. R.)

[Illustration: Encampment of the caterpillar of the small ermine

(_Yponomeuta padella_) on the Siberian crab.]

The caterpillars of other moths, which are in some years very

common--such as the brown-tail (_Porthesia auriflua_), and the

golden-tail (_P. chrysorrhoea_), are also social; and, as the eggs

are hatched late in the summer, the brood passes the winter in a

very closely-woven nest of warm silk. This is usually represented as

composed of leaves which have had their pulpy parts eaten as food by

the colonists; but from minute observation of at least twenty of these

nests in the winter of 1828-9, we are quite satisfied that leaves

are only an accidental, and not a necessary, part of the structure.

When a leaf happens to be in the line of the walls of the nest, it

is included; but there is no apparent design in pressing it into the

service, nor is a branch selected because it is leafy. On the contrary,

by far the greater number of these nests do not contain a single

leaf, but are composed entirely of grey silk. In external form, no

two of these nests are alike; as it depends entirely upon the form of

the branch. When, therefore, there is only one twig, it is somewhat

egg-shaped; but when there are several twigs, it commonly joins each,

assuming an angular shape, as may be seen in the left-hand figure.

[Illustration: Winter nests of _Porthesia chrysorrhoea_, one being

cut open to show the chambers. The dots represent the egesta of the

caterpillars.]

This irregularity arises from the circumstance of each individual

acting on its own account, without the direction or superintendence of

the others. The interior of the structure is, for the same reason, more

regular, being divided into compartments, each of which forms a chamber

for one or more individuals. Previous to the cold weather, these

chambers have but slight partitions; but before the frosts set in the

whole is made thick and warm.

[Illustration: Winter nest of the Social Caterpillars of the Brown-tail

Moth (_Porthesia auriflua_), figured from specimen.]

None of the preceding details, however, appear so striking as what

is recorded of the brown-tail moth (_Porthesia auriflua_) by Mr. W.

Curtis,[EF] whose multitudinous colonies spread great alarm over the

country in the summer of 1782. This alarm was much increased by the

exaggeration and ignorant details which found their way into the

newspapers. The actual numbers of these caterpillars must have been

immense, since Curtis says, "in many of the parishes near London

subscriptions have been opened, and the poor people employed to cut off

the webs at one shilling per bushel, which have been burnt under the

inspection of the church-wardens, overseers, or beadle of the parish:

at the first onset of this business fourscore bushels, as I was most

credibly informed, were collected in one day in the parish of Clapham."

It is not, therefore, very much to be wondered at, that the ignorant,

who are so prone to become the victims of groundless fears, should have

taken serious alarm on having so unusual a phenomenon forced upon their

attention. Some alarmists accordingly asserted that the caterpillars

"were the usual presage of the plague;" and others that they not only

presaged it, but would actually cause it, for "their numbers were great

enough to render the air pestilential;" while, to add to the mischief,

"they would destroy every kind of vegetation, and starve the cattle

in the fields." "Almost every one," adds Curtis, "ignorant of their

history, was under the greatest apprehensions concerning them; so that

even prayers were offered up in some churches to deliver the country

from the apprehended approaching calamity."

It seems to have been either the same caterpillar, or one very

nearly allied to it, probably that of the golden-tail (_Porthesia

chrysorrhoea_), which in 1731-2 produced a similar alarm in France.

Réaumur, on going from Paris to Tours, in September, 1730, found every

oak, great and small, literally swarming with them, and their leaves

parched and brown as if some burning wind had passed over them; for

when newly hatched, like the young buff-tips, they only eat one of the

membranes of the leaf, and of course the other withers away. These

infant legions, under the shelter of their warm nests, survived the

winter in such numbers, that they threatened the destruction not only

of the fruit-trees, but of the forests,--every tree, as Réaumur says,

being overrun with them. The Parliament of Paris thought that ravages

so widely extended loudly called for their interference, and they

accordingly issued an edict, to compel the people to uncaterpillar

(_décheniller_) the trees; which Réaumur ridiculed as impracticable, at

least in the forests. About the middle of May, however, a succession

of cold rains produced so much mortality among the caterpillars, that

the people were happily released from the edict; for it soon became

difficult to find a single individual of the species.[EG] In the same

way the cold rains, during the summer of 1829, seem to have nearly

annihilated the lackeys, which in the early part of the summer swarmed

on every hedge around London. The ignorance displayed in France, at the

time in question, was not inferior to that recorded by Curtis; for the

French journalists gravely asserted that part of the caterpillars were

produced by spiders; and that these spiders, and not the caterpillars,

constructed the webs of the slime of snails, which they were said to

have been seen collecting for the purpose! "Verily," exclaims Réaumur,

"there is more ignorance in our age than one might believe."

It is justly remarked by Curtis, that the caterpillar of the brown-tail

moth is not so limited a feeder as some, nor so indiscriminate as

others; but that it always confines itself to trees or shrubs, and is

never found on herbaceous plants, whose low growth would seldom supply

a suitable foundation for its web. Hence the absurdity of supposing

it would attack the herbage of the field, and produce a famine among

cattle. Curtis says, it is found on the "hawthorn most plentifully, oak

the same, elm very plentifully, most fruit-trees the same, blackthorn

plentifully, rose-trees the same, bramble the same, on the willow and

poplar scarce. None have been noticed on the elder, walnut, ash, fir,

or herbaceous plants. With respect to fruit-trees the injuries they

sustain are most serious, as, in destroying the blossoms as yet in the

bud, they also destroy the fruit in embryo; the owners of orchards,

therefore, have great reason to be alarmed."

The sudden appearance of great numbers of these caterpillars in

particular years, and their scarcity in others, is in some degree

explained by a fact stated by Mr. Salisbury. "A gentleman of Chelsea,"

he says, "has informed me that he once took a nest of moths and bred

them; that some of the eggs came the first year, some the second, and

others of the same nest did not hatch till the third season."[EH] We

reared, during 1829, several nests both of the brown-tails and of

the golden-tails, and a number of the females deposited their eggs

in our nurse-cages; but, contrary to the experiment just quoted, all

of these were hatched during the same autumn. (J. R.) The difference

of temperature and moisture in particular seasons may produce this

diversity.

A no less remarkable winter nest, of a small species of social

caterpillar, is described by M. Bonnet, which we omitted to introduce

when treating of the Glanville fritillary. The nest in question is

literally pendulous, being hung from the branch of a fruit tree by

a strong silken thread. It consists of one or two leaves neatly

folded, and held together with silk, in which the caterpillars live

harmoniously together.

[Illustration: Pendulous leaf-nests, from Bonnet.]

In a recently-published volume of 'Travels in Mexico,' we find a very

remarkable account of some pendulous nests of caterpillars, which

appear to be almost as curious as the nests of the pasteboard-making

wasps, described at p. 177. The author of these Travels does not

define the species of caterpillar whose constructions attracted his

observation. He says, "After having ascended for about an hour, we came

to the region of oaks and other majestically tall trees, the names of

which I could not learn. Suspended from their stately branches were

innumerable nests, enclosed, apparently, in white paper bags, in the

manner of bunches of grapes in England, to preserve them from birds and

flies. I had the curiosity to examine one of them, which I found to

contain numberless caterpillars. The texture is so strong that it is

not easily torn; and the interior contained a quantity of green leaves,

to support the numerous progeny within."[EI]

[We will now give a brief account of several foreign insects that are

remarkable for the pendulous nests which they make.

The first of these is built by a hymenopterous insect belonging to the

genus Larrada. It is fastened to the under side of a leaf, and is made

of vegetable fibres, cut up very short, and masticated by the insect,

much like the materials used by the Fungus Ant, described on page 311.

The insect which forms this nest is black in colour and has very thick

legs. The wings are clouded. It is but a small insect, being only

three-eighths of an inch in length. Both nest and insect are in the

collection of Mr. F. Smith, of the British Museum.

[Illustration: Nest of Larrada.]

In the next illustration are seen two nests built by hymenopterous

insects belonging to the hymenopterous genus Polybia. The left-hand

figure represents a nest made by Polybia sedula, a Brazilian insect. It

is fixed to a large leaf, and, as may be seen, has the entrance at the

end of a long neck. The exterior of the nest is a very thin sheet of

pale-brown substance, almost identical with the paper with which our

British wasps make their nests. It is, however, very much stronger and

very much thinner, and is very close in texture, so that it effectually

excludes rain.

[Illustration: Nests of Polybia.]

The right-hand figure shows a nest also brought from Brazil. It has

no neck, the opening being a mere hole beneath. The name Polybia

is derived from two Greek words signifying that many insects live

together, and has been given to the genus on account of the social

habits of its members.

Our next illustration contains some very remarkable nests.

The large central nest is the cocoon of a moth belonging to the genus

Oiketicus, or Housebuilder. There are many species of Housebuilder

moths, and all are remarkable for the fact that the larva never

exhibits itself, but builds a dwelling in which it conceals itself,

just as does the well-known caddis-worm. Indeed the nests of several

Oiketici look exactly as if the dwelling of a caddis-worm had been

greatly enlarged and hung up in a tree.

[Illustration: Nests of Oiketicus, &c.]

The nest of this species, however, differs from that of the common

Oiketicus by being covered with a coating of greyish silk. If we cut

open the silk, we find a great number of little sticks and leaf-stems

crossed on each other, and showing their ends through the silken cover.

Within these defences there is a layer of leaves cut into small pieces,

and lastly comes the cell inhabited by the caterpillar. It is lined

with a silken web similar in character to that on the outside, but

finer, stronger, and whiter The caterpillar is therefore defended by

four distinct barriers. First comes the strong silken web which lines

the cell, and next is the layer of leaf fragments. Outside them comes

the _chevaux de frise_ of crossed sticks, and lastly we have the grey

silken web. This outer wrapper has no connection with the interior of

the cell, and is only lightly attached to the ends of the cross sticks.

Within this curious dwelling the caterpillar conceals the whole of

its body, clinging to the branch or leaf by its feet, and if alarmed

drawing itself up so that the mouth of the cocoon is pressed tightly

against the branch, and effectually conceals even the feet which hold

it.

The other figure on the right hand represents the dwelling of another

Housebuilder caterpillar. It looks very much as if it were made of

drab cloth. The most remarkable point about it is the lower end. When

the insect is within the dwelling the extremity has a spiral twist,

but when the moth has escaped the spiral form is destroyed, and it

appears as represented in the illustration. The female Oiketicus never

attains the winged state nor leaves her house, but lives and dies in

it, almost unchanged in shape. In fact, the adult female is even more

undeveloped in appearance than the caterpillar, and looks like a large,

fat, unwieldy grub, covered with down. The male, on the contrary, is

a tolerably active moth, with sharply-pointed wings and beautiful

feathered antennæ.

Another kind of Housebuilder's residence is shown in the lower

left-hand figure, enveloped and almost concealed by leaves.

The remaining figures represent the dwellings of two unknown insects,

both from Australia. The upper left-hand nest is made wonderfully like

that of the weaver-bird, being composed of fibres like cow-hairs woven

loosely together. It is brown outside and white in the interior.

The last nest is made of some substance which is smooth, and hard as

horn, brown within, and dark grey on the outside. The circular lid by

which the enclosed insect escapes is shown open.

In the accompanying illustration, we have five remarkable pensile nests

of insects, some British, and others exotic.

Fig. 1 represents the nest of a Pelopæus from Natal. It is made of

dried cow-dung, and is fixed to straws. The length is from three to

five inches, and there are sometimes found three or more in a row upon

a single straw. The insect is about an inch in length, black-blue in

colour, and with clouded wings. The abdomen is small, sharply pointed,

and placed on a long footstalk.

[Illustration: Nests of Pelopæus (1, 2); Anthidium (3); Trypoxylon (4);

and Eumenes (5).]

At Fig. 2 is seen the nest of _Pelopæus Flavipes_, a North American

insect, which is also fixed along its whole length to the supporting

object, which is sometimes a wall, and sometimes, as in the

illustration, a branch. It is made of mud, and the insects seem to have

a sort of gregarious instinct, loving to fix their nests in rows, one

above the other. There is only one larva in each cell. The Pelopæi are,

by the way, allied to the English genus _Ammophila_.

Fig. 3 shows the nest of _Anthidium cordatum_, one of the solitary bees

of Natal. It is made of vegetable fibres. The insect as well as the

nest is represented of the natural size. It is black and shining, with

the under part and sides and legs yellowish.

At Fig. 4 are seen three of the nests of _Trypoxylon aurifrons_, a

Brazilian insect. They are built of mud, and are remarkable for their

elegant shape, which looks as if it had been formed by the hand of the

potter, and for the manner in which the mouth is turned over so as to

form a distinct neck. The larvæ is fed with a store of spiders. The

insect is represented of the natural size; its colour is black, and the

face is covered with short golden hairs, a fact which has gained for it

the name of aurifrons, or golden-fronted.

Our last example, Fig. 5, is the nest of an English insect, _Eumenes

coarctata_. The insect is represented of its natural size. It is very

pretty in colour as well as elegant in shape, being black, diversified

with yellow bands and spots. The nest is made of clay, and is found

upon the heath twigs. The larvæ of the Eumenes are fed with those of

a species of _Crambus_. The insect is tolerably common in Surrey and

Hampshire, and appears in July and August.

The three figures in the next illustration represent the cocoons of

three species of the Bombycidæ, and are given in order to show the

different modes by which they are fastened. The upper nest is hung by a

slight cord, which spreads into a broad silken band wrapped round the

branch for some distance. The right-hand figure shows a very remarkable

cocoon suspended by a long footstalk affixed to a ring. The remarkable

point in the construction of this ring is that it is very hard and

horny, and is not fastened to the branch, but passes loosely round it,

so that the cocoon swings backwards and forwards in the breeze. The

cocoon is about two inches in length, and is covered with thick black

veinings. The lowermost cocoon is most curiously fixed to the branch by

bending the leaves round the exterior of the dwelling, and fixing them

to it with silk. All these specimens were brought from Northern India.]

[Illustration: Bombycidæ.]

In all the nests of social caterpillars, care is taken to leave

apertures for passing out and in. It is remarkable, also, that however

far they may ramble from their nest, they never fail to find their way

back when a shower of rain or nightfall renders shelter necessary. It

requires no great shrewdness to discover how they effect this: for by

looking closely at their track it will be found that it is carpeted

with silk--no individual moving an inch without constructing such a

pathway, both for the use of his companions and to facilitate his own

return. All these social caterpillars, therefore, move more or less

in processional order, each following the road which the first chance

traveller has marked out with his strip of silk carpeting.

[Illustration: Nest and order of marching of the Processionary

Caterpillars of the oak (_Cnethocampa processionea_).]

There are some species, however, which are more remarkable than others

in the regularity of their processional marchings, particularly two

which are found in the south of Europe, but are not indigenous in

Britain. The one named by Réaumur the Processionary (_Cnethocampa

processionea_, Stephens) feeds upon the oak; a brood dividing, when

newly hatched, into one or more parties of several hundred individuals,

which afterwards unite in constructing a common nest nearly two feet

long, and from four to six inches in diameter. As it is not divided

like that of the brown-tails into chambers, but consists of one large

hall, it is not necessary that there should be more openings than one;

and accordingly, when an individual goes out and carpets a path, the

whole colony instinctively follow in the same track, though from the

immense population they are often compelled to march in parallel files

from two to six deep. The procession is always headed by a single

caterpillar; sometimes the leader is immediately followed by one or

two in single file, and sometimes by two abreast, as represented

in the cut. A similar procedure is followed by a species of social

caterpillars which feed on the pine in Savoy and Languedoc; and though

their nests are not half the size of the preceding, they are more

worthy of notice, from the strong and excellent quality of their silk,

which Réaumur was of opinion might be advantageously manufactured.

Their nest consists of more chambers than one, but is furnished with

a main entrance, through which the colonists conduct their foraging

processions.

[In the accompanying illustration is shown a nest of the Processionary

caterpillar, part of which has been torn away to show the interior.

Inside may be seen the larva of a certain beetle (_Calosoma

sycophanta_), which feeds on these caterpillars, and one of the beetles

is seen below in the act of ascending the tree. This beetle, although

exceedingly scarce in England, is very common on the Continent, and

trees have been cleared of Processionary caterpillars by the simple

process of putting a few female beetles upon the branches.]

[Illustration: Nest of Processionary Caterpillars (_Cnethocampa_ and

_Calosoma_).]

_CHAPTER XVIII._

STRUCTURES OF SPIDERS.

Modern naturalists do not rank spiders among insects, because they have

no antennæ, and no division between the head and the shoulders. They

breathe by leaf-shaped gills, situated under the belly, instead of

spiracles in the sides; have a heart connected with these; have eight

legs instead of six; and eight fixed eyes. But as spiders are popularly

considered insects, it will sufficiently suit our purpose to introduce

them here as such.

The apparatus by which spiders construct their ingenious fabrics is

much more complicated than that which we have described as common

to the various species of caterpillars. Caterpillars have only two

reservoirs for the materials of their silk; but spiders, according to

the dissections of M. Treviranus, have four principal vessels, two

larger and two smaller, with a number of minute ones at their base.

Several small tubes branch towards the reservoirs, for carrying to

them, no doubt, a supply of the secreted material. Swammerdam describes

them as twisted into many coils of an agate colour.[EJ] We do not find

them coiled, but nearly straight, and of a deep-yellow colour. From

these, when broken, threads can be drawn out like those spun by the

spider, though we cannot draw them so fine by many degrees.

From these little flasks or bags of gum, situated near the apex of the

abdomen, and not at the mouth, as in caterpillars, a tube originates,

and terminates in the external spinnerets, which may be seen by the

naked eye in the larger spiders, in the form of five little teats

surrounded by a circle, as represented in the following figure.

[Illustration: Garden Spider (_Epeira diadema_), suspended by a thread

proceeding from its spinneret.]

We have seen that the silken thread of a caterpillar is composed

of two united within the tube of the spinneret, but the spider's

thread would appear, from the first view of its five spinnerets, to

be quintuple, and in some species which have six teats, so many times

more. It is not safe, however, in our interpretations of nature to

proceed upon conjecture, however plausible, nor to take anything for

granted which we have not actually seen; since our inferences in such

cases are almost certain to be erroneous. If Aristotle, for example,

had ever looked narrowly at a spider when spinning, he could not have

fancied, as he does, that the materials which it uses are nothing but

wool stripped from its body. On looking, then, with a strong magnifying

glass, at the teat-shaped spinnerets of a spider, we perceive them

studded with regular rows of minute bristle-like points, about a

thousand to each teat, making in all from five to six thousand. These

are minute tubes which we may appropriately term _spinnerules_, as

each is connected with the internal reservoirs, and emits a thread

of inconceivable fineness. In the following figure, this wonderful

apparatus is represented as it appears in the microscope.

[Illustration: Spinnerets of a Spider magnified to show the

_Spinnerules_.]

We do not recollect that naturalists have ventured to assign any cause

for this very remarkable multiplicity of the spinnerules of spiders, so

different from the simple spinneret of caterpillars. To us it appears

to be an admirable provision for their mode of life. Caterpillars

neither require such strong materials, nor that their thread should

dry as quickly. It is well known in our manufactures, particularly

in rope-spinning, that in cords of equal thickness, those which are

composed of many smaller ones united are greatly stronger than those

which are spun at once. In the instance of the spider's thread, this

principle must hold still more strikingly, inasmuch as it is composed

of fluid materials that require to be dried rapidly, and this drying

must be greatly facilitated by exposing so many to the air separately

before their union, which is effected at the distance of about a tenth

of an inch from the spinnerets. In the following figure each of the

threads represented is reckoned to contain one hundred minute threads,

the whole forming only one of the spider's common threads.

Leeuwenhoeck, in one of his extraordinary microscopical observations on

a young spider not bigger than a grain of sand, upon enumerating the

threadlets in one of its threads, calculated that it would require

four millions of them to be as thick as a hair of his beard.

[Illustration: A single thread of a Spider, greatly magnified, so that,

for the small space represented, the lines are shown as parallel.]

[Illustration: Attached end of a Spider's thread magnified.]

Another important advantage derived by the spider from the multiplicity

of its threadlets is, that the thread affords a much more secure

attachment to a wall, a branch of a tree, or any other object, than if

it were simple; for, upon pressing the spinneret against the object, as

spiders always do when they fix a thread, the spinnerules are extended

over an area of some diameter, from every hair's-breadth of which a

_strand_, as rope-makers term it, is extended to compound the main

cord. The preceding figure exhibits this ingenious contrivance.

Those who may be curious to examine this contrivance will see it best

when the line is attached to any black object, for the threads, being

whitish, are, in other cases, not so easily perceived.

Shooting of the Lines.

It has long been considered a curious though a difficult investigation,

to determine in what manner spiders, seeing that they are destitute

of wings, transport themselves from tree to tree, across brooks, and

frequently through the air itself, without any apparent starting point.

On looking into the authors who have treated upon this subject, it is

surprising how little there is to be met with that is new, even in the

most recent. Their conclusions, or rather their conjectural opinions,

are, however, worthy of notice; for by unlearning error, we the more

firmly establish truth.

1. One of the earliest notions upon this subject is that of Blancanus,

the commentator on Aristotle, which is partly adopted by Redi, by

Henricus Regius of Utrecht, by Swammerdam,[EK] by Lehmann, and by Kirby

and Spence.[EL] "The spider's thread," says Swammerdam, "is generally

made up of two or more parts, and after descending by such a thread,

it ascends by one only, and is thus enabled to waft itself from one

height or tree to another, even across running waters; the thread it

leaves loose behind it being driven about by the wind, and so fixed

to some other body." "I placed," says Kirby, "the large garden spider

(_Epeira diadema_) upon a stick about a foot long, set upright in a

vessel containing water.... It let itself drop, not by a single thread,

but by _two_, each distant from the other about the twelfth of an

inch, guided, as usual, by one of its hind feet, and one apparently

smaller than the other. When it had suffered itself to descend nearly

to the surface of the water, it stopped short, and by some means, which

I could not distinctly see, broke off, close to the spinners, the

smallest thread, which still adhering by the other end to the top of

the stick, floated in the air, and was so light as to be carried about

by the slightest breath. On approaching a pencil to the loose end of

this line, it did not adhere from mere contact. I therefore twisted it

once or twice round the pencil, and then drew it tight. The spider,

which had previously climbed to the top of the stick, immediately

pulled at it with one of its feet, and finding it sufficiently tense,

crept along it, strengthening it as it proceeded by another thread, and

thus reached the pencil."

We have repeatedly witnessed this occurrence, both in the fields and

when spiders were placed for experiment, as Kirby has described;

but we very much doubt that the thread broken is ever intended as a

bridge cable, or that it would have been so used in that instance, had

it not been artificially fixed and accidentally found again by the

spider. According to our observations, a spider never abandons, for an

instant, the thread which she despatches in quest of an attachment,

but uniformly keeps trying it with her feet, in order to ascertain its

success. We are, therefore, persuaded that when a thread is broken in

the manner above described, it is because it has been spun too weak;

and spiders may often be seen breaking such threads in the process of

netting their webs. (J. R.)

The plan, besides, as explained by these distinguished writers, would

more frequently prove abortive than successful, from the cut thread

not being sufficiently long. They admit, indeed, that spiders' lines

are often found "a yard or two long, fastened to twigs of grass not a

foot in height.... Here, therefore, some other process must have been

used."[EM]

2. Our celebrated English naturalist, Dr. Lister, whose treatise upon

our native spiders has been the basis of every subsequent work on the

subject, maintains that "some spiders shoot out their threads in the

same manner that porcupines do their quills;[EN] that whereas the

quills of the latter are entirely separated from their bodies, when

thus shot out, the threads of the former remain fixed to their anus,

as the sun's rays to its body."[EO] A French periodical writer goes a

little farther, and says, that spiders have the power of shooting out

threads, and directing them at pleasure towards a determined point,

judging of the distance and position of the object by some sense of

which we are ignorant.[EP] Kirby also says, that he once observed a

small garden spider (_Aranea reticulata_) "standing midway on a long

perpendicular fixed thread, and an appearance caught" his "eye, of

what seemed to be the emission of threads." "I, therefore," he adds,

"moved my arm in the direction in which they apparently proceeded,

and, as I had suspected, a floating thread attached itself to my coat,

along which the spider crept. As this was connected with the spinners

of the spider, it could not have been formed" by breaking a "secondary

thread."[EQ] Again, in speaking of the gossamer-spider, he says, "it

first extends its thigh, shank, and foot, into a right line, and then,

elevating its abdomen till it becomes vertical, _shoots its thread_

into the air, and flies off from its station."[ER]

Another distinguished naturalist, Mr. White of Selborne, in speaking

of the gossamer-spider, says, "Every day in fine weather in autumn do

I see these spiders shooting out their webs, and mounting aloft: they

will go off from the finger, if you will take them into your hand.

Last summer, one alighted on my book as I was reading in the parlour;

and running to the top of the page, and _shooting out a web_, took its

departure from thence. But what I most wondered at was, that it went

off with considerable velocity in a place where no air was stirring;

and I am sure I did not assist it with my breath."[ES]

Having so often witnessed the thread set afloat in the air by

spiders, we can readily conceive the way in which those eminent

naturalists were led to suppose it to be ejected by some animal

force acting like a syringe; but as the statement can be completely

disproved by experiment, we shall only at present ask, in the words of

Swammerdam--"how can it be possible that a thread so fine and slender

should be shot out with force enough to divide and pass through the

air?--is it not rather probable that the air would stop its progress,

and so entangle it and fit it to perplex the spider's operations?"[ET]

The opinion, indeed, is equally improbable with another, suggested by

Dr. Lister, that the spider can retract her thread within the abdomen,

after it has been emitted.[EU] De Geer[EV] very justly joins Swammerdam

in rejecting both of these fancies, which, in our own earlier

observations upon spiders, certainly struck us as plausible and true.

There can be no doubt, indeed, that the animal has a voluntary power of

permitting the material to escape, or stopping it at pleasure, but this

power is not projectile.

3. "There are many people," says the Abbé de la Pluche, "who believe

that the spider flies when they see her pass from branch to branch,

and even from one high tree to another; but she transports herself

in this manner: she places herself upon the end of a branch, or some

projecting body, and there fastens her thread; after which, with her

two hind feet, she squeezes her dugs (_spinnerets_), and presses out

one or more threads of two or three ells in length, which she leaves

to float in the air till it be fixed to some particular place."[EW]

Without pretending to have observed this, Swammerdam says, "I can

easily comprehend how spiders, without giving themselves any motion,

may, by only compressing their spinnerets, force out a thread, which

being driven by the wind, may serve to waft them from one place to

another."[EX] Others, proceeding upon a similar notion, give a rather

different account of the matter. "The spider," says Bingley, "fixes one

end of a thread to the place where she stands, and then with her hind

paws draws out several other threads from the nipples, which, being

lengthened out and driven by the wind to some neighbouring tree or

other object, are by their natural clamminess fixed to it."[EY]

Observation gives some plausibility to the latter opinion, as the

spider always actively uses her legs, though not to draw out the

thread, but to ascertain whether it has caught upon any object. The

notion of her pressing the spinneret with her feet must be a mere

fancy; at least it is not countenanced by anything which we have

observed.

4. An opinion much more recondite is mentioned, if it was not started,

by M. D'Isjonval, that the floating of the spider's thread is

electrical. "Frogs, cats, and other animals," he says, "are affected

by natural electricity, and feel the change of weather; but no other

animal more than myself and my spiders." During wet and windy weather

he accordingly found that they spun very short lines, "but when a

spider spins a long thread, there is a certainty of fine weather for

at least ten or twelve days afterwards."[EZ] A periodical writer, who

signs himself Carolan,[FA] fancies that in darting out her thread the

spider emits a stream of air, or some subtle electric fluid, by which

she guides it as if by magic.

A living writer (Mr. John Murray), whose learning and skill in

conducting experiments give no little weight to his opinions, has

carried these views considerably farther. "The aëronautic spider," he

says, "can propel its thread both horizontally and vertically, and at

all relative angles, in motionless air, and in an atmosphere agitated

by winds; nay more, the aërial traveller can even dart its thread, to

use a nautical phrase, in the 'wind's eye.' My opinion and observations

are based on many hundred experiments.... The entire phenomena are

electrical. When a thread is propelled in a vertical plane, it remains

perpendicular to the horizontal plane, always upright, and when others

are projected at angles more or less inclined, their direction is

invariably preserved; the threads never intermingle, and when a pencil

of threads is propelled, it ever presents the appearance of a divergent

brush. These are electrical phenomena, and cannot be explained but on

electrical principles."

"In clear, fine weather, the air is invariably positive; and it is

precisely in such weather that the aëronautic spider makes its ascent

most easily and rapidly, whether it be in summer or in winter." "When

the air is weakly positive, the ascent of the spider will be difficult,

and its altitude extremely limited, and the threads propelled will

be but little elevated above the horizontal plane. When negative

electricity prevails, as in cloudy weather, or on the approach of rain,

and the index of De Saussure's hygrometer rapidly advancing towards

humidity, the spider is unable to ascend."[FB]

Mr. Murray had previously told us, that "when a stick of excited

sealing-wax is brought near the thread of suspension, it is evidently

repelled; consequently, the electricity of the thread is of a negative

character," while "an excited glass tube brought near, seemed to

attract the thread, and with it the aëronautic spider."[FC] His friend,

Mr. Bowman, further describes the aërial spider as "shooting out four

or five, often six or eight, extremely fine webs several yards long,

which waved in the breeze, diverging from each other like a pencil of

rays." One of them "had two distinct and widely-diverging fasciculi of

webs," and "a line uniting them would have been at right angles to the

direction of the breeze."[FD]

Such is the chief evidence in support of the electrical theory; but

though we have tried these experiments, we have not succeeded in

verifying any one of them. The following statements of Mr. Blackwall

come nearer our own observations.

5. "Having procured a small branched twig," says Mr. Blackwall, "I

fixed it upright in an earthen vessel containing water, its base being

immersed in the liquid, and upon it I placed several of the spiders

which produce gossamer. Whenever the insects thus circumstanced were

exposed to a current of air, either naturally or artificially produced,

they directly turned the thorax towards the quarter whence it came,

even when it was so slight as scarcely to be perceptible, and elevating

the abdomen, they emitted from their spinners a small portion of

glutinous matter, which was instantly carried out in a line, consisting

of four finer ones, with a velocity equal, or nearly so, to that with

which the air moved, as was apparent from observations made on the

motion of detached lines similarly exposed. The spiders, in the next

place, carefully ascertained whether their lines had become firmly

attached to any object or not, by pulling at them with the first pair

of legs; and if the result was satisfactory, after tightening them

sufficiently, they made them pass to the twig; then discharging from

their spinners, which they applied to the spot where they stood, a

little more of their liquid gum, and committing themselves to these

bridges of their own constructing, they passed over them in safety,

drawing a second line after them, as a security in case the first gave

way, and so effected their escape.

"Such was invariably the result when spiders were placed where the air

was liable to be sensibly agitated: I resolved, therefore, to put a

bell-glass over them; and in this situation they remained seventeen

days, evidently unable to produce a single line by which they could

quit the branch they occupied, without encountering the water at its

base; though, on the removal of the glass, they regained their liberty

with as much celerity as in the instances already recorded.

"This experiment, which, from want of due precaution, has misled so

many distinguished naturalists, I have tried with several geometric

spiders, and always with the same success."[FE]

Mr. Blackwall, from subsequent experiments, says he is "confident

in affirming, that in motionless air spiders have not the power of

darting their threads even through the space of half an inch."[FF]

The following details are given in confirmation of this opinion. Mr.

Blackwall observed, the 1st Oct., 1826, a little before noon, with the

sun shining brightly, no wind stirring, and the thermometer in the

shade ranging from 55°·5 to 64°, a profusion of shining lines crossing

each other at every angle, forming a confused net-work, covering

the fields and hedges, and thickly coating his feet and ankles, as

he walked across a pasture. He was more struck with the phenomenon,

because on the previous day a strong gale of wind had blown from the

south, and as gossamer is only seen in calm weather, it must have been

all produced within a very short time.

"What more particularly arrested my attention," says Mr. Blackwall,

"was the ascent of an amazing quantity of webs, of an irregular,

complicated structure, resembling ravelled silk of the finest quality

and clearest white; they were of various shapes and dimensions, some of

the largest measuring upwards of a yard in length, and several inches

in breadth in the widest part; while others were almost as broad as

long, presenting an area of a few square inches only.

"These webs, it was quickly perceived, were not formed in the air, as

is generally believed, but at the earth's surface. The lines of which

they were composed, being brought into contact by the mechanical action

of gentle airs, adhered together, till, by continual additions, they

were accumulated into flakes or masses of considerable magnitude, on

which the ascending current, occasioned by the rarefaction of the

air contiguous to the heated ground, acted with so much force as to

separate them from the objects to which they were attached, raising

them in the atmosphere to a perpendicular height of at least several

hundred feet. I collected a number of these webs about mid-day, as they

rose; and again in the afternoon, when the upward current had ceased,

and they were falling; but scarcely one in twenty contained a spider:

though, on minute inspection, I found small winged insects, chiefly

aphides, entangled in most of them.

"From contemplating this unusual display of gossamer, my thoughts were

naturally directed to the animals which produced it, and the countless

myriads in which they swarmed almost created as much surprise as the

singular occupation that engrossed them. Apparently actuated by the

same impulse, all were intent upon traversing the regions of air:

accordingly, after gaining the summits of various objects, as blades of

grass, stubble, rails, gates, &c., by the slow and laborious process

of climbing, they raised themselves still higher by straightening

their limbs; and elevating the abdomen, by bringing it from the usual

horizontal position into one almost perpendicular, they emitted from

their spinning apparatus a small quantity of the glutinous secretion

with which they construct their webs. This viscous substance being

drawn out by the ascending current of rarefied air into fine lines

several feet in length, was carried upward, until the spiders, feeling

themselves acted upon with sufficient force in that direction, quitted

their hold of the objects on which they stood, and commenced their

journey by mounting aloft.

"Whenever the lines became inadequate to the purpose for which they

were intended, by adhering to any fixed body, they were immediately

detached from the spinners, and so converted into terrestrial gossamer,

by means of the last pair of legs, and the proceedings just described

were repeated; which plainly proves that these operations result from

a strong desire felt by the insects to effect an ascent."[FG] Mr.

Blackwall has recently read a paper (still unpublished) in the Linnean

Society, confirmatory of his opinions.

6. Without going into the particulars of what agrees or disagrees

in the above experiments with our own observations, we shall give a

brief account of what we have actually seen in our researches. (J.

R.) So far as we have determined, then, all the various species of

spiders, how different soever the form of their webs may be, proceed

in the circumstance of shooting their lines precisely alike; but

those which we have found the most manageable in experimenting, are

the small gossamer spider (_Aranea obtextrix_, Bechstein), known by

its shining blackish-brown body and reddish-brown semi-transparent

legs; but particularly the long-bodied spider (_Tetragnatha extensa_,

Latr.), which varies in colour from green to brownish or grey--but has

always a black line along the belly, with a silvery white or yellowish

one on each side. The latter is chiefly recommended by being a very

industrious and persevering spinner, while its movements are easily

seen, from the long cylindrical form of its body and the length of its

legs.

We placed the above two species with five or six others, including

the garden, the domestic and the labyrinthic spiders, in empty

wine-glasses, set in tea-saucers filled with water to prevent their

escape. When they discovered, by repeated descents from the brims of

the glasses, that they were thus surrounded by a wet ditch, they all

set themselves to the task of throwing their silken bridges across. For

this purpose they first endeavoured to ascertain in what direction the

wind blew, or rather (as the experiment was made in our study) which

way any current of air set,--by elevating their arms as we have seen

sailors do in a dead calm. But, as it may prove more interesting to

keep to one individual, we shall first watch the proceedings of the

gossamer spider.

Finding no current of air on any quarter of the brim of the glass, it

seemed to give up all hopes of constructing its bridge of escape, and

placed itself in the attitude of repose; but no sooner did we produce

a stream of air, by blowing gently towards its position, than, fixing

a thread to the glass, and laying hold of it with one of its feet, by

way of security, it placed its body in a vertical position, with its

spinnerets extended outwards; and immediately we had the pleasure of

seeing a thread streaming out from them several feet in length, on

which the little aëronaut sprung up into the air. We were convinced,

from what we thus observed, that it was the double or bend of the

thread which was blown into the air; and we assigned as a reason for

her previously attaching and drawing out a thread from the glass, the

wish to give the wind a _point d'appui_--something upon which it might

have a _purchase_, as a mechanic would say of a lever. The bend of the

thread, then, on this view of the matter, would be carried out by the

wind,--would form the point of impulsion,--and, of course, the escape

bridge would be an ordinary line doubled.

Such was our conclusion, which was strongly corroborated by what we

subsequently found said by M. Latreille--than whom no higher authority

could be given. "When the animal," says he, "desires to cross a brook,

she fixes to a tree or some other object one of the ends of her first

threads, in order that the wind or a current of air may carry the other

end beyond the obstacle;"[FH] and as one end is always attached to the

spinnerets, he must mean that the double of the thread flies off. In

his previous publications, however, Latreille had contented himself

with copying the statement of Dr. Lister.

In order to ascertain the fact, and put an end to all doubts, we

watched, with great care and minuteness, the proceedings of the

long-bodied spider above mentioned, by producing a stream of air

in the same manner, as it perambulated the brim of the glass. It

immediately, as the other had done, attached a thread, and raised

its body perpendicularly, like a tumbler, standing on his hands with

his head downwards; but we looked in vain for this thread bending,

as we had at first supposed, and going off double. Instead of this

it remained tight, while another thread, or what appeared to be so,

streamed off from the spinners, similar to smoke issuing through a

pin-hole, sometimes in a line, and sometimes at a considerable angle,

with the first, according to the current of the air,--the first thread,

extended from the glass to the spinnerets, remaining all the while

tight drawn in a right line. It further appeared to us, that the

first thread proceeded from the pair of spinnerets nearest the head,

while the floating thread came from the outer pair,--though it is

possible in such minute objects we may have been deceived. That the

first was continuous with the second, without any perceptible joining,

we ascertained in numerous instances, by catching the floating line

and pulling it tight, in which case the spider glides along without

attaching another line to the glass; but if she has to coil up the

floating line to tighten it, as usually happens, she gathers it into

a packet and glues the two ends tight together. Her body, while

the floating line streamed out, remained quite motionless, but we

distinctly saw the spinnerets not only projected, as is always done

when a spider spins, but moved in the same way as an infant moves its

lips when sucking. We cannot doubt, therefore, that this motion is

intended to emit (if _eject_ or _project_ be deemed too strong words)

the liquid material of the thread; at the same time, we are quite

certain that it cannot throw out a single inch of thread without the

aid of a current of air. A long-bodied spider will thus throw out in

succession as many threads as we please, by simply blowing towards it;

but not one where there is no current, as under a bell-glass, where it

may be kept till it die, without being able to construct a bridge over

water of an inch long. We never observed more than one floating thread

produced at the same time; though other observers mention several.

The probable commencement, we think, of the floating line, is by the

emission of little globules of the glutinous material to the points of

the spinnerules--perhaps it may be dropped from them, if not ejected,

and the globules being carried off by the current of air, drawn out

into a thread. But we give this as only a conjecture, for we could not

bring a glass of sufficient power to bear upon the spinnerules at the

commencement of the floating line.

In subsequent experiments we found that it was not indispensable for

the spider to rest upon a solid body when producing a line, as she can

do so while she is suspended in the air by another line. When the

current of air also is strong, she will sometimes commit herself to it

by swinging from the end of the line. We have even remarked this when

there was scarcely a breath of air.

We tried another experiment. We pressed pretty firmly upon the base of

the spinnerets, so as not to injure the spider, blowing obliquely over

them; but no floating line appeared. We then touched them with a pencil

and drew out several lines an inch or two in length, upon which we blew

in order to extend them; but in this also we were unsuccessful, as they

did not lengthen more than a quarter of an inch. We next traced out

the reservoirs of a garden-spider (_Epeira diadema_), and immediately

taking a drop of the matter from one of them on the point of a fine

needle, we directed upon it a strong current of air, and succeeded in

blowing out a thick yellow line, as we might have done with gum-water,

of about an inch and a half long.

When we observed our long-bodied spider eager to throw a line by

raising up its body, we brought within three inches of its spinnerets

an excited stick of sealing-wax, of which it took no notice, nor did

any thread extend to it, not even when brought almost to touch the

spinnerets. We had the same want of success with an excited glass rod;

and indeed we had not anticipated any other result, as we have never

observed that these either attract or repel the floating threads,

as Mr. Murray has seen them do; nor have we ever seen the end of a

floating thread separated into its component threadlets and diverging

like a brush, as he and Mr. Bowman describe. It may be proper to

mention that Mr. Murray, in conformity with his theory, explains the

shooting of lines in a current of air by the electric state produced by

motion in consequence of the mutual friction of the gaseous particles.

But this view of the matter does not seem to affect our statements.

Nests, Webs, and Nets of Spiders.

The neatest, though the smallest spider's nest which we have seen, was

constructed in the chink of a garden post, which we had cut out in

the previous summer in getting at the cells of a carpenter-bee. The

architect was one of the large hunting-spiders, erroneously said by

some naturalists to be incapable of spinning. The nest in question was

about two inches high, composed of a very close satin-like texture.

There were two parallel chambers placed perpendicularly, in which

position also the inhabitant reposed there during the day, going, as we

presume, only abroad to prey during the night. But the most remarkable

circumstance was, that the openings (two above and two below) were so

elastic, that they shut almost as closely as the boat cocoon of the

_Tortrix Chlorana_. We observed this spider for several months, but at

last it disappeared, and we took the nest out, under the notion that

it might contain eggs; but we found none, and therefore conclude that

it was only used as a day retreat. (J. R.) The account which Evelyn

has given of these hunting-spiders is so interesting, that we must

transcribe it.

"Of all sorts of insects," says he, "there is none has afforded me

more divertisement than the _venatores_ (hunters), which are a sort of

_lupi_ (wolves) that have their dens in rugged walls and crevices of

our houses; a small brown and delicately-spotted kind of spiders, whose

hinder legs are longer than the rest. Such I did frequently observe

at Rome, which, espying a fly at three or four yards' distance, upon

the balcony where I stood, would not make directly to her, but crawl

under the rail till, being arrived at the antipodes, it would steal

up, seldom missing its aim; but if it chanced to want anything of

being perfectly opposite, would, at first peep, immediately slide down

again,--till, taking better notice, it would come the next time exactly

upon the fly's back: but if this happened not to be within a competent

leap, then would this insect move so softly, as the very shadow of the

gnomon seemed not to be more imperceptible, unless the fly moved; and

then would the spider move also in the same proportion, keeping that

just time with her motion, as if the same soul had animated both these

little bodies; and whether it were forwards, backwards, or to either

side, without at all turning her body like a well-managed horse: but

if the capricious fly took wing and pitched upon another place behind

our huntress, then would the spider whirl its body so nimbly about, as

nothing could be imagined more swift: by which means she always kept

the head towards her prey, though, to appearance, as immovable as if

it had been a nail driven into the wood, till by that indiscernible

progress (being arrived within the sphere of her reach) she made a

fatal leap, swift as lightning, upon the fly, catching him in the pole,

where she never quitted hold till her belly was full, and then carried

the remainder home."

One feels a little sceptical, however, when he adds, "I have beheld

them instructing their young ones how to hunt, which they would

sometimes discipline for not well observing; but when any of the old

ones did (as sometimes) miss a leap, they would run out of the field

and hide themselves in their crannies, as ashamed, and haply not

to be seen abroad for four or five hours after; for so long have I

watched the nature of this strange insect, the contemplation of whose

so wonderful sagacity and address has amazed me; nor do I find in any

chase whatsoever more cunning and stratagem observed. I have found some

of these spiders in my garden, when the weather, towards spring, is

very hot, but they are nothing so eager in hunting as in Italy."[FI]

We have only to add to this lively narrative, that the hunting-spider,

when he leaps, takes good care to provide against accidental falls by

always swinging himself from a good strong cable of silk, as Swammerdam

correctly states,[FJ] and which anybody may verify, as one of the

small hunters (_Salticus scenicus_), known by having its back striped

with black and white like a zebra, is very common in Britain.

Mr. Weston, the editor of 'Bloomfield's Remains,' falls into a

very singular mistake about hunting-spiders, imagining them to be

web-weaving ones which have exhausted their materials, and which are

therefore compelled to hunt. In proof of this he gives an instance

which fell under his own observation![FK]

As a contrast to the little elastic satin nest of the hunter, we

may mention the largest with which we are acquainted,--that of the

labyrinthic spider (_Agelena labyrinthica_, Walchenaer). Our readers

must often have seen this nest spread out like a broad sheet in hedges,

furze, and other low bushes, and sometimes on the ground. The middle

of this sheet, which is of a close texture, is swung like a sailor's

hammock, by silken ropes extended all around to the higher branches;

but the whole curves upwards and backwards, sloping down to a long

funnel-shaped gallery which is nearly horizontal at the entrance, but

soon winds obliquely till it becomes quite perpendicular. This curved

gallery is about a quarter of an inch in diameter, is much more closely

woven than the sheet part of the web, and sometimes descends into a

hole in the ground, though oftener into a group of crowded twigs, or a

tuft of grass. Here the spider dwells secure, frequently resting with

her legs extended from the entrance of the gallery, ready to spring out

upon whatever insect may fall into her sheet net. She herself can only

be caught by getting behind her and forcing her out into the web; but

though we have often endeavoured to make her construct a nest under our

eye, we have been as unsuccessful as in similar experiments with the

common house spider (_Aranea domestica_). (J. R.)

The house spider's proceedings were long ago described by Homberg,

and the account has been copied, as usual, by almost every subsequent

writer. Goldsmith has, indeed, given some strange misstatements from

his own observations, and Bingley has added the original remark, that,

after fixing its first thread, creeping along the wall, and joining

it as it proceeds, it "_darts itself to the opposite side_, where

the other end is to be fastened!"[FL] Homberg's spider took the more

circuitous route of travelling to the opposite wall, carrying in one

of the claws the end of the thread previously fixed, lest it should

stick in the wrong place. This we believe to be the correct statement,

for as the web is always horizontal, it would seldom answer to commit

a floating thread to the wind, as is done by other species. Homberg's

spider, after stretching as many lines by way of _warp_ as it deemed

sufficient between the two walls of the corner which it had chosen,

proceeded to cross this in the way our weavers do in adding the _woof_,

with this difference, that the spider's threads were only laid on, and

not interlaced.[FM] The domestic spiders, however, in these modern

days, must have forgot this mode of weaving, for none of their webs

will be found to be thus regularly constructed!

The geometric, or net-working spiders (_Tendeuses_, Latr.), are as well

known in most districts as any of the preceding; almost every bush and

tree in the gardens and hedge-rows having one or more of their nets

stretched out in a vertical position between adjacent branches. The

common garden spider (_Epeira diadema_), and the long-bodied spider

(_Tetragnatha extensa_), are the best known of this order.

The chief care of a spider of this sort is, to form a cable of

sufficient strength to bear the net she means to hang upon it; and,

after throwing out a floating line as above described, when it catches

properly she doubles and redoubles it with additional threads. On

trying its strength she is not contented with the test of pulling it

with her legs, but drops herself down several feet from various points

of it, as we have often seen, swinging and bobbing with the whole

weight of her body. She proceeds in a similar manner with the rest of

the framework of her wheel-shaped net; and it may be remarked that some

of the ends of these lines are not simple, but in form of a Y, giving

her the additional security of two attachments instead of one.

[Illustration: Geometric Net of _Epeira diadema_.]

In constructing the body of the net, the most remarkable circumstance

is her using her limbs as a measure, to regulate the distances of her

_radii_ or wheel-spokes, and the circular meshes interweaved into them.

These are consequently always proportional to the size of the spider.

She often takes up her station in the centre, but not always, though

it is so said by inaccurate writers; for she as frequently lurks in a

little chamber constructed under a leaf or other shelter at the corner

of her web, ready to dart down upon whatever prey may be entangled in

her net. The centre of the net is said also to be composed of more

viscid materials than its suspensory lines,--a circumstance alleged to

be proved by the former appearing under the microscope studded with

globules of gum.[FN] We have not been able to verify this distinction,

having seen the suspensory lines as often studded in this manner as

those in the centre. (J. R.)

Mason-Spiders.