VIEW THE MOBILE VERSION of www.bugsinsects.net Informational Site Network Informational
Privacy
   Home - Articles - Books

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.





Next: THE LEAF-CUTTERS

Previous: INSTINCT AND DISCERNMENT



Add to del.icio.us Add to Reddit Add to Digg Add to Del.icio.us Add to Google Add to Twitter Add to Stumble Upon
Add to Informational Site Network
Report
Privacy
SHAREADD TO EBOOK