ECONOMY OF ENERGY





What stimulus does the insect obey when it employs the reserve powers

that slumber in its race? Of what use are its industrial variations?

The Osmia will yield us her secret with no great difficulty. Let us

examine her work in a cylindrical habitation. I have described in

full detail, in the foregoing pages, the structure of her nests when

the dwelling adopted is a reed-stump or any other cylinder; and I

will content myself here with recapitulating the essential features

of that nest-building.



We must first distinguish three classes of reeds according to their

diameter: the small, the medium-sized and the large. I call small

those whose narrow width just allows the Osmia to go about her

household duties without discomfort. She must be able to turn where

she stands in order to brush her abdomen and rub off its load of

pollen, after disgorging the honey in the centre of the heap of flour

already collected. If the width of the tube does not admit of this

operation, if the insect is obliged to go out and then come in again

backwards in order to place itself in a favourable posture for the

discharge of the pollen, then the reed is too narrow and the Osmia is

rather reluctant to accept it. The middle-sized reeds and a fortiori

the large ones leave the victualler entire liberty of action; but the

former do not exceed the width of a cell, a width agreeing with the

bulk of the future cocoon, whereas the latter, with their excessive

diameter, require more than one chamber on the same floor.



When free to choose, the Osmia settles by preference in the small

reeds. Here, the work of building is reduced to its simplest

expression and consists in dividing the tube by means of earthen

partitions into a straight row of cells. Against the partition

forming the back wall of the preceding cell the mother places first a

heap of honey and pollen; next, when the portion is seen to be

enough, she lays an egg in the centre of it. Then and then only she

resumes her plasterer's work and marks out the length of the new cell

with a mud partition. This partition in its turn serves as the rear-

wall of another chamber, which is first victualled and then closed;

and so on until the cylinder is sufficiently colonized and receives a

thick terminal stopper at its orifice. In a word, the chief

characteristic of this method of nest-building, the roughest of all,

is that the partition in front is not undertaken so long as the

victualling is still incomplete, or, in other words, that the

provisions and the egg are deposited before the Bee sets to work on

the partition.



At first sight, this latter detail hardly deserves attention: is it

not right to fill the pot before we put a lid on? The Osmia who owns

a medium-sized reed is not at all of this opinion; and other

plasterers share her views, as we shall see when we watch the

Odynerus building her nest. (A genus of Mason-wasps, the essays on

which have not yet been translated into English.--Translator's Note.)

Here we have an excellent illustration of one of those latent powers

held in reserve for exceptional occasions and suddenly brought into

play, although often very far removed from the insect's regular

methods. If the reed, without being of inordinate width from the

point of view of the cocoon, is nevertheless too spacious to afford

the Bee a suitable purchase against the wall at the moment when she

is disgorging honey and brushing off her load of pollen; the Osmia

altogether changes the order of her work; she sets up the partition

first and then does the victualling.



All round the inside of the tube she places a ring of mud, which, as

the result of her constant visits to the mortar, ends by becoming a

complete diaphragm minus an orifice at the side, a sort of round dog-

hole, just large enough for the insect to pass through. When the cell

is thus marked out and almost wholly closed, the Osmia attends to the

storing of her provisions and the laying of her eggs. Steadying

herself against the margin of the hole at one time with her fore-legs

and at another with her hind-legs, she is able to empty her crop and

to brush her abdomen; by pressing against it, she obtains a foothold

for her little efforts in these various operations. When the tube was

narrow, the outer wall supplied this foothold and the earthen

partition was postponed until the heap of provisions was completed

and surmounted by the egg; but in the present case the passage is too

wide and would leave the insect floundering helplessly in space, so

the partition with its serving-hatch takes precedence of the

victuals. This method is a little more expensive than the other,

first in materials, because of the diameter of the reed, and secondly

in time, if only because of the dog-hole, a delicate piece of mortar-

work which is too soft at first and cannot be used until it has dried

and become harder. Therefore the Osmia, who is sparing of her time

and strength, accepts medium-sized reeds only when there are no small

ones available.



The large tubes she will use only in grave emergencies and I am

unable to state exactly what these exceptional circumstances are.

Perhaps she decides to make use of those roomy dwellings when the

eggs have to be laid at once and there is no other shelter in the

neighbourhood. While my cylinder-hives gave me plenty of well-filled

reeds of the first and second class, they provided me with but half-

a-dozen at most of the third, notwithstanding my precaution to

furnish the apparatus with a varied assortment.



The Osmia's repugnance to big cylinders is quite justified. The work

in fact is longer and more costly when the tubes are wide. An

inspection of a nest constructed under these conditions is enough to

convince us. It now consists not of a string of chambers obtained by

simple transverse partitions, but of a confused heap of clumsy, many-

sided compartments, standing back to back, with a tendency to group

themselves in storeys without succeeding in doing so, because any

regular arrangement would mean that the ceilings possessed a span

which it is not in the builder's power to achieve. The edifice is not

a geometrical masterpiece and it is even less satisfactory from the

point of view of economy. In the previous constructions, the sides of

the reed supplied the greater part of the walls and the work was

limited to one partition for each cell. Here, except at the actual

periphery, where the tube itself supplies a foundation, everything

has to be obtained by sheer building: the floor, the ceiling, the

walls of the many-sided compartment are one and all made of mortar.

The structure is almost as costly in materials as that of the

Chalicodoma or the Pelopaeus.



It must be pretty difficult, too, when one thinks of its

irregularity. Fitting as best she can the projecting angles of the

new cell into the recessed corners of the cell already built, the

Osmia runs up walls more or less curved, upright or slanting, which

intersect one another at various points, so that each compartment

requires a new and complicated plan of construction, which is very

different from the circular-partition style of architecture, with its

row of parallel dividing-disks. Moreover, in this composite

arrangement, the size of the recesses left available by the earlier

work to some extent decides the assessment of the sexes, for,

according to the dimensions of those recesses, the walls erected take

in now a larger space, the home of a female, and now a smaller space,

the home of a male. Roomy quarters therefore have a double drawback

for the Osmia: they greatly increase the outlay in materials; and

also they establish in the lower layers, among the females, males

who, because of their earlier hatching, would be much better placed

near the mouth of the nest. I am convinced of it: if the Osmia

refuses big reeds and accepts them only in the last resort, when

there are no others, it is because she objects to additional labour

and to the mixture of the sexes.



The Snail-shell, then, is but an indifferent home for her, which she

is quite ready to abandon should a better offer. Its expanding cavity

represents an average between the favourite small cylinder and the

unpopular large cylinder, which is accepted only when there is no

other obtainable. The first whorls of the spiral are too narrow to be

of use to the Osmia, but the middle ones have the right diameter for

cocoons arranged in single file. Here things happen as in a first-

class reed, for the helical curve in no way affects the method of

structure employed for a rectilinear series of cells. Circular

partitions are erected at the required distances, with or without a

serving-hatch, according to the diameter. These mark out the first

cells, one after the other, which are reserved solely for the

females. Then comes the last whorl, which is much too wide for a

single row of cells; and here we once more find, exactly as in a wide

reed, a costly profusion of masonry, an irregular arrangement of the

cells and a mixture of the sexes.



Having said so much, let us go back to the Osmia of the quarries.

Why, when I offer them simultaneously Snail-shells and reeds of a

suitable size, do the old frequenters of the shells prefer the reeds,

which in all probability have never before been utilized by their

race? Most of them scorn the ancestral dwelling and enthusiastically

accept my reeds. Some, it is true, take up their quarters in the

Snail-shell; but even among these a goodly number refuse my new

shells and return to their birth-place, the old Snail-shell, in order

to utilize the family property, without much labour, at the cost of a

few repairs. Whence, I ask, comes this general preference for the

cylinder, never used hitherto? The answer can be only this: of two

lodgings at her disposal the Osmia selects the one that provides a

comfortable home at a minimum outlay. She economizes her strength

when restoring an old nest; she economizes it when replacing the

Snail-shell by the reed.



Can animal industry, like our own, obey the law of economy, the

sovran law that governs our industrial machine even as it governs, at

least to all appearances, the sublime machine of the universe? Let us

go deeper into the question and bring other workers into evidence,

those especially who, better equipped perhaps and at any rate better

fitted for hard work, attack the difficulties of their trade boldly

and look down upon alien establishments with scorn. Of this number

are the Chalicodomae, the Mason-bees proper.



The Mason-bee of the Pebbles does not make up her mind to build a

brand-new dome unless there be a dearth of old and not quite

dilapidated nests. The mothers, sisters apparently and heirs-at-law

to the domain, dispute fiercely for the ancestral abode. The first

who, by sheer brute force, takes possession of the dome, perches upon

it and, for long hours, watches events while polishing her wings. If

some claimant puts in an appearance, forthwith the other turns her

out with a volley of blows. In this way the old nests are employed so

long as they have not become uninhabitable hovels.



Without being equally jealous of the maternal inheritance, the Mason-

bee of the Sheds eagerly uses the cells whence her generation issued.

The work in the huge city under the eaves begins thus: the old cells,

of which, by the way, the good-natured owner yields a portion to

Latreille's Osmia and to the Three-horned Osmia alike, are first made

clean and wholesome and cleared of broken plaster and then

provisioned and shut. When all the accessible chambers are occupied,

the actual building begins with a new stratum of cells upon the

former edifice, which becomes more and more massive from year to

year.



The Mason-bee of the Shrubs, with her spherical nests hardly larger

than walnuts, puzzled me at first. Does she use the old buildings or

does she abandon them for good? To-day perplexity makes way for

certainty: she uses them very readily. I have several times surprised

her lodging her family in the empty rooms of a nest where she was

doubtless born herself. Like her kinswoman of the Pebbles, she

returns to the native dwelling and fights for its possession. Also,

like the dome-builder, she is an anchorite and prefers to cultivate

the lean inheritance alone. Sometimes, however, the nest is of

exceptional size and harbours a crowd of occupants, who live in

peace, each attending to her business, as in the colossal hives in

the sheds. Should the colony be at all numerous and the estate

descend to two or three generations in succession, with a fresh layer

of masonry each year, the normal walnut-sized nest becomes a ball as

large as a man's two fists. I have gathered on a pine-tree a nest of

the Mason-bee of the Shrubs that weighed a kilogram (2.205 pounds

avoirdupois.--Translator's Note.) and was the size of a child's head.

A twig hardly thicker than a straw served as its support. The casual

sight of that lump swinging over the spot on which I had sat down

made me think of the mishap that befell Garo. (The hero of La

Fontaine's fable, "Le Gland et la Citrouille," who wondered why

acorns grew on such tall trees and pumpkins on such low vines, until

he fell asleep under one of the latter and a pumpkin dropped upon his

nose.--Translator's Note.) If such nests were plentiful in the trees,

any one seeking the shade would run a serious risk of having his head

smashed.



After the Masons, the Carpenters. Among the guild of wood-workers,

the most powerful is the Carpenter-bee (Xylocopa violacea (Cf. "The

Life of the Spider": chapter 1.--Translator's Note.)), a very large

Bee of formidable appearance, clad in black velvet with violet-

coloured wings. The mother gives her larvae as a dwelling a

cylindrical gallery which she digs in rotten wood. Useless timber

lying exposed to the air, vine-poles, large logs of fire-wood

seasoning out of doors, heaped up in front of the farmhouse porch,

stumps of trees, vine-stocks and big branches of all kinds are her

favourite building-yards. A solitary and industrious worker, she

bores, bit by bit, circular passages the width of one's thumb, as

clear-cut as though they were made with an auger. A heap of saw-dust

accumulates on the ground and bears witness to the severity of the

task. Usually, the same aperture is the entrance to two or three

parallel corridors. With several galleries there is accommodation for

the entire laying, though each gallery is quite short; and the Bee

thus avoids those long series which always create difficulties when

the moment of hatching arrives. The laggards and the insects eager to

emerge are less likely to get in each other's way.



After obtaining the dwelling, the Carpenter-bee behaves like the

Osmia who is in possession of a reed. Provisions are collected, the

egg is laid and the chamber is walled in front with a saw-dust

partition. The work is pursued in this way until the two or three

passages composing the house are completely stocked. Heaping up

provisions and erecting partitions are an invariable feature of the

Xylocopa's programme; no circumstance can release the mother from the

duty of providing for the future of her family, in the matter both of

ready-prepared food and of separate compartments for the rearing of

each larva. It is only in the boring of the galleries, the most

laborious part of the work, that economy can occasionally be

exercised by a piece of luck. Well, is the powerful Carpenter, all

unheeding of fatigue, able to take advantage of such fortunate

occasions? Does she know how to make use of houses which she has not

tunnelled herself? Why, yes: a free lodging suits her just as much as

it does the various Mason-bees. She knows as well as they the

economic advantages of an old nest that is still in good condition:

she settles down, as far as possible, in her predecessors' galleries,

after freshening up the sides with a superficial scraping. And she

does better still. She readily accepts lodgings which have never

known a drill, no matter whose. The stout reeds used in the trellis-

work that supports the vines are valuable discoveries, providing as

they do sumptuous galleries free of cost. No preliminary work or next

to none is required with these. Indeed, the insect does not even

trouble to make a side-opening, which would enable it to occupy the

cavity contained within two nodes; it prefers the opening at the end

cut by man's pruning-knife. If the next partition be too near to give

a chamber of sufficient length, the Xylocopa destroys it, which is

easy work, not to be compared with the labour of cutting an entrance

through the side. In this way, a spacious gallery, following on the

short vestibule made by the pruning-knife, is obtained with the least

possible expenditure of energy.



Guided by what was happening on the trellises, I offered the black

Bee the hospitality of my reed-hives. From the very beginning, the

insect gladly welcomed my advances; each spring, I see it inspect my

rows of cylinders, pick out the best ones and instal itself there.

Its work, reduced to a minimum by my intervention, is limited to the

partitions, the materials for which are obtained by scraping the

inner sides of the reed.



As first-rate joiners, next to the Carpenter-bees come the Lithurgi,

of whom my district possesses two species: L. cornutus, FAB., and L.

chrysurus, BOY. By what aberration of nomenclature was the name of

Lithurgus, a worker in stone, given to insects which work solely in

wood? I have caught the first, the stronger of the two, digging

galleries in a large block of oak that served as an arch for a

stable-door; I have always found the second, who is more widely

distributed, settling in dead wood--mulberry, cherry, almond, poplar-

-that was still standing. Her work is exactly the same as the

Xylocopa's, on a smaller scale. A single entrance-hole gives access

to three or four parallel galleries, assembled in a serried group;

and these galleries are subdivided into cells by means of saw-dust

partitions. Following the example of the big Carpenter-bee, Lithurgus

chrysurus knows how to avoid the laborious work of boring, when

occasion offers: I find her cocoons lodged almost as often in old

dormitories as in new ones. She too has the tendency to economize her

strength by turning the work of her predecessors to account. I do not

despair of seeing her adopt the reed if, one day, when I possess a

large enough colony, I decide to try this experiment on her. I will

say nothing about L. cornutus, whom I only once surprised at her

carpentering.



The Anthophorae, those children of the precipitous earthy banks, show

the same thrifty spirit as the other members of the mining

corporation. Three species, A. parietina, A. personata and A.

pilipes, dig long corridors leading to the cells, which are scattered

here and there and one by one. These passages remain open at all

seasons of the year. When spring comes, the new colony uses them just

as they are, provided that they are well preserved in the clayey mass

baked by the sun; it increases their length if necessary, runs out a

few more branches, but does not decide to start boring in new ground

until the old city, which, with its many labyrinths, resembles some

monstrous sponge, is too much undermined for safety. The oval niches,

the cells that open on those corridors, are also profitably employed.

The Anthophora restores their entrance, which has been destroyed by

the insect's recent emergence; she smooths their walls with a fresh

coat of whitewash, after which the lodging is fit to receive the heap

of honey and the egg. When the old cells, insufficient in number and

moreover partly inhabited by diverse intruders, are all occupied, the

boring of new cells begins, in the extended sections of the

galleries, and the rest of the eggs are housed. In this way, the

swarm is settled at a minimum of expense.



To conclude this brief account, let us change the zoological setting

and, as we have already spoken of the Sparrow, see what he can do as

a builder. The simplest form of his nest is the great round ball of

straw, dead leaves and feathers, in the fork of a few branches. It is

costly in material, but can be set up anywhere, when the hole in the

wall or the shelter of a tile are lacking. What reasons induced him

to give up the spherical edifice? To all seeming, the same reasons

that led the Osmia to abandon the Snail-shell's spiral, which

requires a fatiguing expenditure of clay, in favour of the economical

cylinder of the reed. By making his home in a hole in the wall, the

Sparrow escapes the greater part of his work. Here, the dome that

serves as a protection from the rain and the thick walls that offer

resistance to the wind both become superfluous. A mere mattress is

sufficient; the cavity in the wall provides the rest. The saving is

great; and the Sparrow appreciates it quite as much as the Osmia.



This does not mean that the primitive art has disappeared, lost

through neglect; it remains an ineffaceable characteristic of the

species, ever ready to declare itself should circumstances demand it.

The generations of to-day are as much endowed with it as the

generations of yore; without apprenticeship, without the example of

others, they have within themselves, in the potential state, the

industrial aptitude of their ancestors. If aroused by the stimulus of

necessity, this aptitude will pass suddenly from inaction to action.

When, therefore, the Sparrow still from time to time indulges in

spherical building, this is not progress on his part, as is sometimes

contended; it is, on the contrary, a retrogression, a return to the

ancient customs, so prodigal of labour. He is behaving like the Osmia

who, in default of a reed, makes shift with a Snail-shell, which is

more difficult to utilize but easier to find. The cylinder and the

hole in the wall stand for progress; the spiral of the Snail-shell

and the ball-shaped nest represent the starting-point.



I have, I think, sufficiently illustrated the inference which is

borne out by the whole mass of analogous facts. Animal industry

manifests a tendency to achieve the essential with a minimum of

expenditure; after its own fashion, the insect bears witness to the

economy of energy. On the one hand, instinct imposes upon it a craft

that is unchangeable in its fundamental features; on the other hand,

it is left a certain latitude in the details, so as to take advantage

of favourable circumstances and attain the object aimed at with the

least possible expenditure of time, materials and work, the three

elements of mechanical labour. The problem in higher geometry solved

by the Hive-bee is only a particular case--true, a magnificent case,-

-of this general law of economy which seems to govern the whole

animal world. The wax cells, with their maximum capacity as against a

minimum wall-space, are the equivalent, with the superaddition of a

marvellous scientific skill, of the Osmia's compartments in which the

stonework is reduced to a minimum through the selection of a reed.

The artificer in mud and the artificer in wax obey the same tendency:

they economize. Do they know what they are doing? Who would venture

to suggest it in the case of the Bee grappling with her

transcendental problem? The others, pursuing their rustic art, are no

wiser. With all of them, there is no calculation, no premeditation,

but simply blind obedience to the law of general harmony.





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