THE PRESERVATION OF THE INDIVIDUAL AND THE PRESERVATION OF THE SPECIES — FOODS MANUFACTURED BY THE PARENTS FOR THEIR YOUNG — SPECIES WHICH OBTAIN FOR THEIR LARVÆ FOODS MANUFACTURED BY OTHERS — CARCASSES OF ANIMALS STORED UP — PROVISION OF PARALYSED LIVING ANIMALS — THE CAUSE OF THE PARALYSIS — THE SURENESS OF INSTINCT — SIMILAR CASES IN WHICH THE SPECIFIC INSTINCT IS LESS POWERFUL AND INDIVIDUAL INITIATIVE GREATER — GENERA LESS SKILFUL IN THE ART OF PARALYSING VICTIMS.

The preservation of the individual and the preservation of the species. — In the previous chapter we have seen animals preparing for the future, and amassing materials for their own subsistence. In other cases these provisions are destined to feed the young. It is the same industry, sometimes exercised for the preservation of the individual, sometimes for the perpetuation of the race. We must expect to find acts of the last kind more instinctive and less reflective than those of the first, and this agrees well with what we know of natural selection. If we now see living beings display so many resources and calculate with such certainty all that will favour the healthy development of their descendants, we must not necessarily conclude that the species possess these instincts from the beginning. They are not to be regarded as mechanisms artfully wound up and functioning since the appearance of life on the earth with the same inevitable regularity. The qualities which we find in them were weak at first; they have developed in the course of ages, and have finally, by heredity, been impressed upon the creatures to manifest themselves by necessary acts from which there is no longer any escape. There is no need for surprise if we meet to-day, I do not say among all, but among a very large number of animals, this foresight for offspring in a well-marked form. It is easy to understand that the species that first acquired and fixed an instinct propitious to the increase of the race has rapidly prospered, stifling beneath its extension those that are less favoured from this point of view, which is of capital importance in a struggle for a place beneath the sun. At the present day if the struggle of animal life offers few facts of lack of foresight for the rearing of young, it is because this defect has killed the races who were subject to it; they have disappeared, or have only been saved by qualities of another order.

For the rest, if it is difficult to reconstitute except in imagination the different stages through which, in time, and in a determined species, acts at first imperfect, but designed, have become perfect and instinctive, we can at least find in space different degrees of the same instinct in allied genera which lead us by a succession of transitions from mechanical action to reflective action.

As I cannot quote all the facts showing this care for the future, I will select a few. It must be said at first that a considerable number of animals show nothing of the kind. Let us leave aside all the inferior beings to speak of those among whom we may expect some degree of method. Crustacea, fish, Batrachians, and many others lay their eggs, are contented to conceal them a little so that they may not become a too easy prey, and are altogether indifferent as to what may happen afterwards. As soon as they come out, the young obtain their own food from day to day; myriads are destroyed, and if the races remain so strong numerically it is because they are saved by the innumerable quantity of eggs produced by a single female. If it were not for this prodigious fecundity these species would have disappeared. Birds make no provision for their young; but, on the other hand, as long as the latter are weak and unable to obtain their own prey, the parents feed them every day by hunting both for themselves and the brood.

I will not insist on those beings who, like mammals, produce physiological reserves, not for their own use, but for the profit of their young. The females of these animals elaborate materials from their own organism and store them up in the form of milk to nourish the young. This fact is related to foresight, with a view to offspring, exactly in the same way as the Honey Ants show a transformation of foresight for the individual. In both cases industry is replaced by the function of a specially adapted organ.

Foods manufactured by the parents for the young. — It is especially insects with whose industries we are here concerned, and they are more or less instinctive in various cases. Every one knows how the Hymenoptera prepare honey from the pollen of flowers, to some extent for themselves, but especially in order that their young may at the moment of appearance possess a food which will enable them to undergo their first metamorphosis sheltered from the inclemencies outside. These foods are enclosed with great art, according to the species, either in skilfully-constructed cells of wax, as by Bees, or in nests of paper or cardboard which the Wasps fabricate, or again in huts built of earth in the manner of the Chalicodoma.

Species which obtain for their larvÆ foods manufactured by others. — Other insects have not this taste for lengthy labours, and do not know how to execute them; but they do not intend that their young shall be the victims of maternal lack of skill, and they display marvellous resources to enable them to profit by the foresight of others.

The Sitaris muralis, a beetle whose customs have been described by Fabre in a remarkable manner,71 may be counted among the cleverest in assuring to its larvÆ the goods of others. It puts them in a position to profit by it, and when they are installed they know sufficiently well what to do. The species has so long perpetuated itself by this process that it has become, both in mother and offspring, highly automatic. It is a hymenopterous insect which this family, whose first vital manifestation is theft, thus levies a contribution on. It is called the Anthophora pilifera, and during the fine weather it makes a collection of honey intended to be absorbed by its own larvÆ, if it had not the misfortune to be watched by one of these intriguing Coleoptera. Wherever in Provence there is a perpendicular wall, natural or artificial, a little cliff, a sloping ditch, or the wall of one of those caves which the people of the country use for putting their tools in, the Anthophora hollows out galleries, at the bottom of which he builds a certain number of chambers. He fills each of them with honey, places in it an egg which floats in the midst of this little lake of nectar, and closes it all up. The Sitaris covets this honey to nourish its offspring, and the chamber to shelter it. After having discovered one of the galleries of which I have spoken, the female Sitaris comes about the beginning of September to lay her eggs, which are numerous, being not generally fewer than two thousand. In the following month the larvÆ appear; they are black, and swarm in a little heap mixed up with the remains of egg-shells. They vegetate in this condition for a long time, and may still be found there in May. At this period they have become more active, and, in order to complete their development, are thinking of profiting by their favourable situation near the entrance to a gallery of the Hymenoptera; when a male Anthophora comes within reach, two or three of them catch hold of him and climb on to his thorax. They maintain themselves there by clinging to the hairs. At the moment of fertilisation the male, thus burdened, comes in contact with the female; the coleopterous larvÆ then pass on to her, so that, according to Fabre’s expression, the meeting of the sexes brings death and life to the eggs at the same time. Henceforth fixed on this laying insect, the little Sitaris remain quiet, and have only to wait; their future is assured. The Anthophora has made her chambers, and with the greatest care has filled each of them with honey. Then in the midst she deposits an egg, which remains floating on the surface like a little boat; when her task is accomplished, the mother passes to a new cell to confide to it another of her descendants. During this time the parasite larva hastily descends the abdominal hairs and allows itself to fall on the egg of the Anthophora, to be then borne upon it as upon a raft; its fall must take place at the precise instant which will enable it to embark without falling into the honey, in which just now it would be glued fast, and perish. This series of circumstances results only in the introduction of a single Sitaris into a chamber; the moment which must be profited by is too short for many of them to seize. If the female Anthophora carries others hidden in her hairs, they are obliged to await a new hatching to let themselves glide off. Thus enclosed with the egg of the Anthophora and its provision of honey, the larva has no other rival to fear, and may alone utilise the whole store. This parasitism has to such an extent become a habit with the species, that the larva’s organisation has become modified by it. At the moment when it falls into the cell it cannot feed on honey. It is indispensable for its development that it should first devour the egg on which it floats; it can at this period be nourished by no other food. In acting in this way it also frees itself from a voracious being who would require much food. This first repast lasts about eight days, at the end of which it undergoes a moult, takes another form, and begins to float on the honey, gradually devouring it, for at this stage it becomes able to assimilate honey. Slowly its development is completed, with extremely interesting details with which we need not now concern ourselves. The larva of Sitaris is then in conditions exceptionally favourable for growth; but, in spite of appearances, there is no reason for admiring the marvellous foresight and extraordinary sureness of instinct; nearly everything depends on a fortuitous circumstance, a chance. This becomes very evident if we study another related beetle; it is called the Sitaris colletis, and lives at the expense of the hymenopterous Colletes, as its relative at the expense of the Anthophora. But these two species of the same genus are very unequally aided by chance. The one whose history we have just traced attaches itself to an insect whose egg floats above a store of honey; the second chooses a victim who attaches its egg to the walls of a chamber. (Fig. 15.) This almost insignificant difference has a considerable influence on the parasite’s evolution. In the first case it is alone, and may develop with certainty; in the second, on the contrary, several Sitaris penetrate the chamber and climb up to attack the egg, which in this case also must be their first food. This rivalry causes a struggle to the death. If one of the larvÆ is notably more vigorous than its rivals, it may free itself from them and survive. Let us consider the fate in store for the two species. The first is much more favoured, since a happy chance permits each germ to produce an individual; in the second, each individual which completes its evolution deprives several of its brothers of life. And even this only happens in the most favourable cases, for it may be that not one Sitaris in the chamber may reach the adult state. If the first arrival begins to absorb the egg of the Colletes, a second hungry one may kill it in the midst of its repast and take its place. But the conqueror finds the provisions already reduced and insufficient to enable it to reach the moulting stage, at the end of which it could profit by the honey. Ill-nourished and weakened, it cannot support this crisis, and its corpse falls beside that of its fellow whom it had sacrificed. Three or four parasites may thus succeed to the same feast, and the victory of the last is useless to him. His first struggle for life and his first triumph are followed by irreparable defeat. These two examples show very well how a slight difference may favour a species, and how a happy quality is capable of being perpetuated by heredity, since by its very nature it is destined to be extended to more numerous beings.

Carcasses of animals stored up. — These insects lay up for their offspring stores manufactured by themselves or by others. The class we are now about to consider makes provision of animals either dead or in a torpid condition, with more or less art and more or less sure instinct. Most people have seen the Necrophorus or Burying Beetle working in fields or gardens. These are large Coleoptera who feed on abandoned carrion; everything is good to them — bodies of small mammals, birds, or frogs; they are very easy to please, and as long as the beast is dead that is all they require. When they have found such remains, and consider only how to satisfy their hunger, they do not take much trouble, and gnaw the prey on the spot where they have found it. They are not alone at the feast, and in spite of their diligence numerous rivals come up to dispute it; it is necessary to share with a great number of noisy and voracious flies and insects. In the adult state they come out well from this competition; but as good parents they wish to save their larvÆ from it, as in a feeble condition these might suffer severely. They desire to lay up a carcass for their young alone, and with this object they bury it in the earth. The eggs also which will thus develop in the soil have more chance of escaping destruction by various insectivorous animals. If these diggers find a rat (Fig. 16) or a dead bird, three or four unite their efforts, glide beneath it, and dig with immense activity, kicking away with their hind legs the earth withdrawn from the hole. They do not pause, and their work soon perceptibly advances. The rat gradually sinks in the pit as it grows deeper. When they have the good fortune to find the earth soft they can sink the prey in less than two hours to a depth of thirty centimetres. At this level they stop, and throw back into the hole the earth they have dug out, carefully smoothing the hillock which covers the grave. Thus stored up, the carcass is ready to receive the Necrophorus eggs. The females enter the soil and lay on the buried mammal; then they retire, satisfied to leave their little ones, when they appear, face to face with such abundant nourishment. When they emerge from the envelope the young larvÆ find themselves in the presence of this stored food, which has been softened by putrefaction and rendered more easy of digestion. If the treasure has not fallen on a spot easy to dig, the Necrophorus quickly recognise the fact, and do not waste time in useless labour. Endowed with considerable strength relatively to their size, three or four of them creep beneath the prey, and co-ordinating their efforts they transport it several metres off to a spot which they know by experience to be suitable for their labours. It may happen that soft earth is too far away, and transport becoming too difficult a task, they renounce it. But as good food should never be wasted, they utilise it by feeding themselves, awaiting a more manageable god-send for their offspring.

Many observers have studied these beetles, and all are surprised at their sagacity, and the way in which their various operations are adapted to circumstances; genuine reflection governs their acts, which are always combined to produce a definite effect.

Provision of paralysed living animals. — It is unnecessary to say how much better it would be for the young larva to have at its disposal instead of a carcass a living animal, but paralysed and rendered motionless by some method. It is difficult to believe the thing possible, yet nothing is better established. There is a hymenopterous relative of the Wasp called the Sphex. Instead of laying up honey they store animal provisions for their larvÆ. Fabre has studied one of them, the Sphex flavipennis.72 It is in September that this wasp lays her eggs; during this month to shelter her little ones she hollows out a dozen burrows and provisions them. She has then to devote about three days’ work to each of them, for there is much to do, as may be imagined. For each of these hiding-places the Sphex first pierces a horizontal gallery about two or three inches long; then she bends it obliquely so that it penetrates deeply into the earth, and it is again continued in this direction for about three inches. At the end of this passage three or four chambers are made, usually three; each of these is meant to receive one egg. The insect interrupts its mining task, not forming the three chambers consecutively; when the first is completed she provisions it — we shall soon see in what manner — and lays an egg there; then she blocks it up, suppressing all communication between this cell and the gallery; this done she bores a second passage, provisions it, and lays another egg, closes up the orifice, and proceeds to prepare the third. This work is pushed on with great activity, and when completed the Sphex entirely fills up the subterranean passage, and completely isolates the hope of the race at a depth sufficient to shelter it well. A last precaution is taken: before leaving, the rubbish in front of the obstructed opening is cleared away, and every trace of the operation disappears. The nest is then definitely abandoned, and another one prepared.

The chambers in which the larvÆ are enclosed — hastily made with little care, and with rough unsmoothed walls — are not very solid, and could not last long without slipping; but as they only have to last for a single season they possess sufficient resistance for the insect’s purpose. The larva also knows very well how to protect itself against the roughness of the walls, and overlays them with a silky secretion produced by its glands.

We have now to consider the nature of the provisions placed by the Sphex near the egg. Each cell must contain four crickets. That is the amount of food necessary for a larva during its evolution, and these insects are in fact large enough to supply a considerable amount of nourishment. When the Sphex interrupts digging operations it is to fly on a hunting expedition. It soon returns with a cricket it has seized, holding it by one antenna which it turns round in its jaws. It is a heavy burden for the slender Sphex to bear. Sometimes on foot, dragging its burden after it, sometimes flying, and carrying the suspended cricket always in a passive condition, the burrow is gradually reached, not without difficulty. In spite of appearances, the cricket is not dead; it cannot move, but if kept for several days it will not putrefy, and its joints remain supple. It is simply the victim of a general paralysis.

The cause of the paralysis. — It was evidently of the greatest interest to know how the Sphex contrived this capture, and what method it used to suppress the movements of the prey. In order to obtain the solution of this problem, Fabre during a long period accumulated experiments and observations, and at last discovered in every detail how the thing was done. In order to compel the Sphex to act in his presence, he placed himself in front of the orifice of a gallery in which the insect was working; he soon saw it returning with a paralysed cricket. Arrived at the burrow, the insect placed the prey on the ground for a moment and disappeared in the passage to see that everything was in order, and that no damage had taken place since its departure. Everything was going well, and it reappeared, took up its burden, and again entered the subterranean passage, drawing the victim along. It brought it into the chamber for which it was destined, placing it on its back, the head down and the feet towards the door. Then it set out hunting again until it had ranged four crickets side by side. Before attempting a decisive experiment, the observer felt his way. At the moment when the Sphex was buried in the earth examining the chamber, Fabre withdrew the prey a short distance and awaited events. Having made the domiciliary visit, the Sphex then went straight to the place where it had left its insect, but could not find it. It was naturally very perplexed, and examined the neighbourhood with extreme agitation, not knowing what had happened, and evidently regarding the whole affair as very extraordinary; at last it found the victim it was seeking. The cricket still preserved the same immobility; its executioner seized it by an antenna and drew it anew to the entrance of the hole. In the interior of the subterranean domain everything is in good order; the insect had just assured itself of the fact, and we should expect to see it enter with its prey; not at all, it entered alone, and only decided to introduce the prey after it had made a fresh inspection. This fact is surprising, and it is still more surprising that if the practical joke of removing the cricket is repeated several times in succession, the Sphex drags it anew every time to the entrance of the burrow and first descends alone; forty times over this experiment succeeded without the insect deciding to renounce the habitual manoeuvre. Fabre insists on this fact, and rightly, for nothing should be neglected; he makes it a text to show how automatic instinct is, and how the acts which proceed from it are invariably regulated so as to succeed one another always in the same order. In their nature these acts are quite indistinguishable from intelligent acts; only the creature is not capable of modifying them to bring them into harmony with unforeseen circumstances. All this is correct, but where it becomes excessive is in endowing animals alone with instinct and separating them from this point of view from Man. It is incontestable that the custom of visiting the burrow before introducing a victim into it has become so imperious in the Sphex that it cannot be broken, even when it is of no use. It is a mechanical instinct. But we may see an exactly parallel manifestation of human intelligence. In face of danger man utters cries of distress; they are heard and assistance comes. But these appeals are not intelligent and appropriate to the end; they are instinctive. Place the same individual in a situation where he knows very well that his voice cannot be heard; this will not hinder him from reproducing the same acts if he finds himself in the presence of danger. It is thus that the Sphex proceeds, guided by instincts, and it is no reason for despising it. And even in the course of this little experiment the insect gives proof of judgment. When it finds its cricket, it is perfectly aware that it is the same cricket which it brought, that there is no life in it, and that there is no need to re-commence the struggle; it sees too that it is not an ordinary corpse liable to putrefaction, but the very same cricket, and it does not hesitate to utilise it at once.

These habits being ascertained, Fabre proceeded to find out how the paralysis is produced. He awaited near a burrow the Sphex’s arrival, dragging a victim by an antenna, and while the insect was occupied in the subterranean survey he substituted a living cricket for that which the Sphex had left, expecting to find it on the spot where it had been placed. On emerging it perceives the cricket scampering away; not a moment was to be lost, and without reflection it leapt on the refractory victim. A lively struggle followed, a duel to the death among the blades of grass; it was a truly dramatic spectacle, the agile assailant whirling around the Cricket, who kicked violently with his hind legs. If a blow were to reach the Sphex it would be disembowelled; but it avoids the blows skilfully without ceasing its own violent attack. At last the combat ends; the cricket is brought to earth, turned on to its back, and maintained in this position by the Sphex. Still on its guard, the latter seizes in its jaws one of the filaments which terminate the abdomen of the vanquished, placing its legs on the belly; with the two posterior legs it holds the head turned back so as to stretch the under side of the neck. The cricket is unable to move and the conqueror’s sting wanders over the horny carapace seeking a joint, feeling for a soft place in which it can enter to give the finishing stroke. The dart at last reaches, between the head and the neck, the spot where the hard portions articulate, leaving between them a space without covering. The joint in the armour is found. The Sphex’s abdomen is agitated convulsively; the sting penetrates the skin, piercing a ganglion situated just beneath this point; the venom spreads and acts on the nervous cells, which can no longer convey messages to the muscles. That is not all; the sting wanders over the cricket’s belly, this time seeking the joint between the neck and the thorax; it finds it, and is again thrust in with fury; a second ganglion of the nervous chain is thus perforated and poisoned. After these two wounds the victim is completely paralysed.As already mentioned, several facts enable us to recognise that the Cricket is by no means dead. It is simply incapable of movement, as would happen after an injection of curare. This poison kills a superior animal, for it hinders the muscular movements of the chest and diaphragm, necessary to respiration; but if a frog, which can breathe through its skin, is thus acted on it comes to life again at the end of twenty-four or forty-eight hours if the dose has not been too strong. The cricket is in a similar condition; it neither eats nor breathes; being incapable also of movement, there is no vital expenditure; it remains in a sort of torpor, or latent life, awaiting the tragic fate that is reserved for it. When it has been deposited in the little mortuary chamber the Sphex lays an egg on its thorax. The larva will soon come out to penetrate the body of the prey by enlarging the hole left by the sting. It thus finds for its first meals a food which unites the flavour of living flesh with the immobility of death. Nothing can be more convenient. When the first body is eaten it proceeds to the second, and thus devours successively the four victims stored up by maternal foresight.

In order not to interrupt the description and interfere with the succession of the acts, I have passed without remark the experiment in which Fabre substituted a living animal for the Sphex’s already paralysed captive. It seems to me, however, that in this circumstance the insect showed judgment, and knew how to act in accordance with new requirements. It was evidently the first time in insect memory in which so surprising a phenomenon had been seen as a victim at the last moment again taking the field. We cannot make instinct intervene here. If the Sphex’s acts are so automatic as we are sometimes led to believe, in accordance with facts which are perfectly accurate, we ought always to observe the following succession of acts: first, hollowing of the burrow; second, the chase; third, the blows of the dart; fourth, the different manoeuvres for placing the victim in the sarcophagus. Now in the present case the insect had accomplished the first three series of actions, and had even begun the fourth; it ought next to drag the cricket into the burrow without listening to the recriminations which the latter had no business to make, since it was to be regarded as having received the two routine doses of poison. But the Sphex sees its victim come to life, understands this fact, and without seeking to fathom the cause judges that a new struggle and new blows of the sting are necessary; he understands that it is necessary to begin afresh, since the usual result has not been attained. He is then capable of reflection, and the series of acts which he accomplishes are not ordained with such inflexibility that it is impossible for him to modify them in order to conform them to varying circumstances.

The Sphex occitanica acts in the same manner as its relative in this complicated art of laying up provisions for the family. The differences are only in detail. Instead of hollowing the burrow first and then setting out on the chase to fill it, it does not devote itself to the labour of digging until a successful expedition has already assured the victim. (Fig. 17.) Instead of attacking crickets it seeks a larger orthopterous insect, the Ephippigera. The struggle is no doubt more difficult, but the result is proportionately greater, and the pursuit does not need to be so often renewed; a single captive is sufficient for its larva.73

The sureness of instinct. — It is not doubtful that a sure inherited instinct conducts the Sphex to prick its victim in the situation of the nervous ganglia, which will be wounded in the act. It may be said that the lesion results from the position in which the hymenopterous insect maintains its victim; for the sting is on the median line, and can only penetrate at the soft points; the two points attacked are then rigorously determined by physical circumstances. But these arguments have no bearing if we consider the method of procedure adopted by the Ammophila,74 a hymenopterous insect related to the preceding, which paralyses caterpillars. It is free in this case to insert its sting at any portion of the body; yet it knows how to turn over and arrange the captive so that the dart shall penetrate both times at two points where ganglia will be poisoned and immobility without death be induced. It must then be agreed that there is here an instinct much too sure to be called mechanical; but these facts, which considered alone seem simply marvellous, become much less so, and lend themselves to evolutionary interpretation, when it is recognised that they are related by insensible degrees to other facts of the same order, much more intelligent and at the same time less sure.

Similar cases in which the specific instinct is less powerful and individual initiative greater. — Here is, for instance, the case of the Chlorion, where each animal possesses more considerable initiative.75 It attacks the Cockroach. These insects are of an extremely varied size, according to age, and as they are also very agile the Chlorion is not certain of being always able to obtain victims of the same dimension. The orifice of its burrow, which it hollows in walls between the crevices of the stones, is calculated on the average size of its victims. It has also the habit of paralysing the cockroach by stinging it on the nervous chain. These preliminary operations do not impede it, but it is embarrassed when it wishes to introduce through the entrance of its gallery an insect which is too large. It pulls at first as much as it can, but seeing the failure of its efforts it does not persevere in this attempt, and comes out to survey the situation. Decidedly the victim is too large and cannot pass through. The Chlorion begins by cutting off the elytra, which maintain it rigid and prevent it from being compressed. This done, it harnesses itself anew and re-commences its efforts. But this is not sufficient, and the victim still resists. The insect returns, and again examines the situation. Now it is a leg which is placed cross-ways and opposes the introduction of the body; strong diseases need strong remedies, and our Chlorion sets itself to amputate this encumbering appendage. It triumphs at last; the cockroach yields to its efforts, and little by little penetrates the hole. As may be seen, the labour is laborious and painful, and may present itself beneath various aspects which call for a certain ingenuity on the part of the animal.

Up to recent years the Cerceris was considered to act with as much certainty as the Sphex, and to obey an infallible instinct which always guided it for the best in the interests of its offspring. The insects it attacks belong to the genus Buprestis. It consumes them in considerable numbers. Its manner of action, as described by LÉon Dufour,76 much resembles that of the Sphex, and it would be superfluous to describe it. The only fact which I wish to mention, and which has been put out of doubt by the illustrious naturalist, is this: the Buprestis are paralysed, not dead; all the joints of the antennÆ and legs remain flexible and the intestines in good condition. He was able to dissect some which had been in a state of lethargy for at least a week or a fortnight, although, under normal conditions, these insects in summer decay rapidly, and after forty-eight hours cannot be used for anatomical purposes. Another observer, Paul Marchal, took up this question afresh, and the results which he obtained seemed to indicate an instinct much less firm than earlier studies tended to show.77

Genera less skilful in the art of paralysing victims. — These researches show us that in the Cerceris instinct is still subject to defect. In some neighbouring genera we can seize it, as it were, in process of formation. The way in which the Bembex, or Sand Wasp, provisions burrows by maternal foresight is much less mechanical than that of the Sphex. It is again Fabre who has described with most care the customs of this hymenopterous insect.78 It hollows out for each egg a chamber communicating with the air by a gallery, and performs this work with little care and very roughly. Less skilful than the others, it does not amass at once all the provisions which its larvÆ will need during the period of evolution. When the offspring has absorbed the last prey brought, it is necessary to bring a new victim. This insect is scarcely more advanced than birds, who feed their young from day to day. And it is a great labour to re-open every time the gallery which leads to the nursery; on all these visits, in fact, the Bembex fills it up on leaving, and causes the disappearance of all revealing traces. It is obliged to take so much trouble, because it has not inherited from its ancestors the receipt for the paralysing sting; it throws itself without care on its victim, delivers a few chance blows, and kills it. Necessarily it cannot, under these conditions, lay up provisions for the future; they would corrupt, and the larvÆ would not be benefited; hence the obligation of frequently returning to the nest, and of a perpetual hunt to feed descendants whom nature has gifted with an excellent appetite. According to the age of the offspring, the mother chooses prey of different sizes; at first she brings small Diptera; then, when it has grown, she captures for it large blow-flies, and lastly gadflies.79 It will be seen, then, that if we suppose the instinct of the Sphex to be slowly developed by being derived from a sting given at random, we make a supposition which is quite admissible and rests on ascertained facts. However this may be, the Bembex, returning to its burrow, is able to find it again with marvellous certainty, in spite of the care taken to hide it by removing every trace that might reveal its existence. It is guided by an extraordinary topographic instinct, which men not only do not possess, but cannot even understand the nature of.

It would appear that certain Hymenoptera, fearing to kill their victim with the sting, and not knowing the art of skilful lesions, attempt to immobilise them by wounds of another sort. This is the case with the Pompilius, according to Goureau,80 who has studied it. This insect nourishes its larvÆ with spiders; it seems certain that in most cases the spider is not pricked. Victims who have been taken from the interior of provision burrows can live for a long time in spite of their wounds; they cannot, therefore, have received venom by inoculation. The author already quoted believes that the Pompilius seizes its captive by the pedicle which unites the abdomen to the cephalothorax, and that it triturates this point between its jaws. From this either death or temporary immobility may follow. The Pompilius also makes up for its relative ignorance by considerable ingenuity. Thus sometimes, when it fears a return to life of the victim destined for its larvÆ, it cuts off the legs while it is still passive. Goureau has found in the nest of this insect living spiders with their legs cut off.