INSTINCT AND INTELLIGENCE

OUR study of the activities of wasps has satisfied us that it is impracticable to classify them in any simple way. The old notion that the acts of bees, wasps, and ants were all varying forms of instinct is no longer tenable, and must give way to a more philosophical view. It would appear to be quite certain that there are not only instinctive acts but acts of intelligence as well, and a third variety also—acts that are probably due to imitation, although whether much or little intelligence accompanies this imitation is admittedly difficult to determine. Again, acts that are instinctive in one species may be intelligent in another, and we may even assert that there is a considerable variation in the amount of intelligence displayed by different individuals of the same species. We have met with such difficulty in our attempts to arrange the activities of wasps in different groups that we are forced to the conclusion that any scheme of classification is merely a convenience, useful for purposes of study or generalization, but not to be taken for an absolutely true expression of all the facts. This kind of perplexity is well understood and allowed for in all morphological work, but it has never been fully realized in the study of habits. The explanation is not far to seek. The habits of but few animals have been studied in sufficient detail to bring out the evidence that there is as much variation on the psychological as on the morphological side, although this field seems fresh and inviting when compared with the researches of the laboratory.

The necessity of interpreting the actions of animals in terms of our own consciousness must be always with us. To interpret them at all we must consider what our own mental states would be under similar circumstances, our safeguard being to keep always before us the progressive weakening of the evidence as we apply it to animals whose structure is less and less like our own.

We arrange the activities of the wasps that we have studied into two groups, Instincts, and Acts of Intelligence, it being understood that these classes pass by insensible stages into each other, and that acts that are purely instinctive when performed for the first time are probably in some degree modified by individual experience. In this classification the question of origin is not considered. The facts are grouped under the two heads, the inferences that they warrant being left for later consideration. Under the term Instinct we place all complex acts that are performed previous to experience and in a similar manner by all members of the same sex and race, leaving out as non-essential, at this time, the question of whether they are or are not accompanied by consciousness. Under Intelligence we place those conscious actions which are more or less modifiable by experience. It is this power that enables an insect to seek, accept, refuse, choose,—to decline to make use of this or to turn to account some other thing. Many writers prefer the term Adaptation for these activities, and it possesses certain advantages. With these definitions in mind, let us group the activities of wasps under the two heads.

With the wasps of the genus PelopÆus we were present on several occasions when the young emerged from the pupa case and gnawed their way out of the mud cell. They were limp, and their wings had not perfectly hardened, and yet when we touched them they tried to attack us, thrusting out the sting and moving the abdomen about in various directions. These movements were well directed, and, so far as we could observe, quite as perfect as in the adult wasp. Stinging, then, is an instinctive act.

The particular method of attack and capture practiced by each species in securing its prey is instinctive. Ammophila pricks a number of ganglia along the ventral face of the caterpillar; PelopÆus, we believe, stabs the spider in the cephalothorax, and probably the several species of Pompilus do the same. Astata bicolor adopts the same tactics in capturing her bugs, while it is said of the fly-catchers that they commonly overcome their victims without using the sting. It is by instinct, too, that these wasps take their proper food supply, one worms, another spiders, a third flies, moths, or beetles. So strong and deeply seated is the preference, that no fly robber ever takes spiders, nor will the ravisher of the spiders change to beetles or bugs.ill295

The mode of carrying their booty is a true instinct. Pompilus takes hold of her spider anywhere, but always drags it over the ground, walking backward; Oxybelus clasps her fly with the hind legs, while Bembex uses the second pair to hold hers tightly against the under side of her thorax. Each works after her own fashion, and in a way that is uniform for each species.

The capturing of the victim and caring for it before the hole is made, as in the case of P. quinquenotatus, or the reverse method, pursued by Astata, Ammophila, Bembex, and others, of preparing the nest before the food supply is secured, is certainly instinctive; as is also the way in which some of these wasps act after bringing the prey to the nest. For example, S. ichneumonea places her grasshopper just at the entrance to the excavation, and then enters to see that all is right before dragging it in. Under natural conditions this order is never varied, although the wasp can adapt herself to different circumstances when occasion demands. Again, we see Oxybelus scratching open her nest while on the wing, and entering at once with the fly held tightly in her legs. Each way is characteristic of the species, and would be an important part of any definition of the animal based upon its habits.

The general style of the nest depends upon instinct. Trypoxylon uses hollow passages in trees, posts, straws, or brick walls; Diodontus americanus, a member of the same family, always burrows in the ground, as do Bembex, Ammophila, and Sphex. In the case of Trypoxylon the passage may be ready for use or may require more or less preparation; the instinctive part is the impulse that requires the insect to use a certain kind of habitation. Any one familiar with T. rubrocinctum would never look for her nest in standing stems or under stones; to use Mr. Morgan’s test, he would be willing to bet on the general style of the dwelling-place. All of these acts are similarly performed by individuals of the same sex and race, not in circumstantial detail but quite in the same way in a broad sense. Variation is always present, but the tendency to depart from a certain type is not excessive. In Cerceris the burrow is tortuous, this style of work being common to many species in the genus, and very characteristic. No Sphex nor Ammophila constructs any such tunnel. The adherence of all the members of a species to a certain style of architecture is, then, due to instinct.

The spinning of the cocoon, in those species in which the larva is protected in this manner, and its shape, are instinctive. We find that closely allied species in the same genus make very different cocoons, as is seen in T. rubrocinctum and T. bidentatum. Some wasps spin no such covering for themselves. It is a well-known fact that silkworms sometimes omit the spinning of a cocoon; but this does not affect the argument, since the descendants of these individuals make the characteristic covering. Such cases are probably due to individual variation or perhaps to atavism, this throwing back being not uncommon among forms that are well known.

Not all of the instinctive acts here enumerated are displayed by each species studied, although they are common to most of them. We have doubtless overlooked some activities that should come under this head, as we have not made a thorough study of any sufficient number of species to make a final settlement of the matter.

As we have seen with Ammophila and PelopÆus, faults of instinct are not uncommon, but of all our wasps the one that shows the greatest aberrations is Pompilus biguttatus. The sandy beach of Lake Michigan is a favorite nesting-ground with this species, and is the scene of many a bold robbery, since they are unprincipled little wretches and

“... the good old rule
Sufficeth them, the simple plan
That they should take who have the power
And they should keep who can.”

We once found an unusually tiny biguttatus vainly trying to drag a large Epeirid which her sting had reduced to helplessness. It was as though a feeble child should try to move the body of an elephant. The little wasp clasped one of the spider’s legs firmly in her mandibles, and then with braced feet and the wildest flutter of wings made gallant but futile attempts to get it started. Now she lost her hold on the ground, and wings and legs were all whirling desperately in the air. Now her feet grasped a loose ball of earth, and, feeling that something was moving, she renewed her efforts. The pellet was drawn nearer and began to rotate around the wasp, while she seemed to be under the impression that she was moving forward. After a few minutes of vigorous exercise, she paused, perhaps to see how she was getting on, and the bit of earth rolled away; so that when the attack was renewed, it was under the old discouraging conditions. She was the impersonation of perseverance and energy; but after half an hour (no one knows how long she had been at it before we came) she gave it up, and with many reluctant circlings flew away. It was probably experiences of this kind that developed in some of her relatives the habit of digging the grave under the victim, and thus saving the trouble of transportation.

At another time, we saw a biguttatus trying to run backward with a little bit of a spider, which she had lifted from the ground and was carrying in her mandibles,—trying to run backward, because it is the rule with this genus to move in that way when encumbered with a load, it being easier to drag a heavy spider than to pick it up and go forward. The wasp in question was drawn in two directions. Instinct made her go backward, although in this particular case it was needless, while she felt a constant desire to turn and go straight ahead. As a result she waltzed slowly over the sand in a series of overlapping circles, her head turned toward every point of the compass in succession, a kind of progress most amusing to the lookers-on.

Biguttatus is not strong enough to fly when laden, but it is the habit of the species to climb backwards to the top of every obstacle in the path, and from this vantage point to gain time by taking a downward flight in the direction of the nest. It is only in the case of tall, smooth-stemmed plants and grasses that the advantage gained is enough to repay the trouble of climbing, and we have often thought that the notion costs the wasp more trouble than it is worth,—as was certainly the case with one comical little creature that carried the idea to the extreme of folly. Not only did she scale objects in her way, but just as old Dr. Johnson felt that he had to touch every tree and post as he walked along, so when this wasp saw, out of the corner of her eye, a stone or a plant three or four inches to one side, it called upon her to climb, and climb she did, although she was obliged to leave her proper path to do it.

It is obviously more difficult to distinguish actions of intelligence than of instinct. One must be familiar with the normal conditions of the insects in question before he is able to note those slight changes in the environment that offer some opportunity for an adaptation of means to ends, or before he is competent to devise experiments which will test their powers in this direction.

We find two classes of intelligent actions among the Hymenoptera which are sufficiently distinct to be considered separately, although, like all natural groups, they grade into each other. The first of these includes those actions that are performed by large numbers in a similar fashion under like conditions, while in the second class each act is an individual affair,—as where a single wasp, uninfluenced in any way by the example of those about it, displays unusual intelligence in grappling with the affairs of life. Examples of the first class are found in such modifications of instinct as are shown by PelopÆus and other wasps in the character of their habitations. PelopÆus, instead of building in hollow trees or under shelving rocks, as was the ancient custom of the race, now nests in chimneys, or under the eaves of buildings. We have found T. rubrocinctum taking advantage of the face of a straw-stack that had been cut off smoothly as the cattle were fed through the winter. The same power of adaptation is shown by Fabre’s experiment with Osmia, in which he took two dozen nests in shells from a quarry, where the bees had been nesting for centuries, and placed them in his study along with some empty shells and some hollow stems. When the bees came out, in the spring, nearly all of them selected the stalks to build in as being better suited to their use than the shells. All of these changes are intelligent adaptations to new modes of life, serving to keep the species in harmony with its surroundings. The same thing may be seen when a number of social wasps work together to replace the roof of their nest when it has been torn off.

An instance of the second class is seen in one of our examples of Pompilus marginatus. This species, while searching for a nesting-place, leaves its spider lying on the ground or hides it under a lump of earth, in either of which positions the booty is subject to the attacks of ants; the wasp in question improved upon the custom of her tribe by carrying the spider up into a plant and hanging it there. We have now and then seen a queen of Polistes fusca occupy a comb of the previous year instead of building a new one for herself,—showing a better mental equipment than her sisters who were not strong-minded enough to change their ways, and so built new nests alongside of unoccupied old ones which were in good condition. In Bembex society it is good form to close the door on leaving home, but sometimes a wasp will save time by leaving the entrance open. This, however, is a doubtful case, as the advantage would, perhaps, be more than balanced by the exposure of the nest to parasites.

Some years after our first experience with Pompilus scelestus we saw a wasp of this species carrying her spider home. She dropped it close to the nest, and looked meditatively, first at the hole and then at the spider. It was unquestionably going to be a very tight fit, but if she could get it in that would be an advantage; so after a moment she seized it by the tip of the abdomen and backing down tried to pull it after. Tug—tug! No, it would not go down, and scelestus pushed it out and carried it to a place of safety up among some clover blossoms. She then washed and brushed herself neatly, and took several little walks, so that it was fully fifteen minutes before she began to enlarge her nest. All that time she must have carried in her little scrap of a mind the idea of doing a necessary act which was outside of her ordinary routine; and we noted with interest that the change when it was made accomplished exactly what was needed,—the spider went in, but not too easily.

In an experiment with a French Sphex which has the habit of laying her cricket down at the threshold, and going inside for an instant before dragging it in, Fabre took advantage of the moment that the wasp was out of sight below to move her prey to a little distance, with the result that when the wasp came up she brought her cricket to the same spot and left it as before, while she visited the interior of the nest. Since he repeated this experiment about forty times and always with the same result, it seemed fair to draw the conclusion that nothing less than the performance of a certain series of acts in a certain order would satisfy her impulse. She must place her prey just so close to the doorway; she must then descend to examine the nest; and after that she must at once drag it down, any disturbance of this routine causing her to refuse to proceed. We once found a Sphex ichneumonea at work storing her nest, and thought it would be interesting to pursue Fabre’s method and find out whether she were equally persistent in following her regular routine. We allowed her to carry in one grasshopper to establish her normal method of procedure, and found that, bringing it on the wing, she dropped it about six inches away, ran into the nest, out again and over to the grasshopper, which she straddled and carried by the head to the entrance. She then ran down head first, turned around, came up, and seizing it by the head, pulled it within. On the following day, when she had brought a grasshopper to the entrance of the nest, and while she was below, we moved it back five or six inches. When she came out, she carried it to the same spot and went down as before. We removed it again, with the same result, and the performance was repeated a third and a fourth time, but the fifth time that she had found her prey where we had placed it she seized it by the head, and going backward dragged it down into the nest without pausing. On the next day the experiment was repeated. After we had moved the grasshopper away four times, she carried it into the nest, going head foremost. On the fourth and last day of our experiment, she replaced the grasshopper at the door of the nest and ran inside seven times, but then seized it and dragged it in, going backward. How shall this change in a long-established custom be explained, except by saying that her intelligence led her to adapt herself to circumstances? She was enough of a conservative to prefer the old way, but was not such a slave to custom as to be unable to vary it.

“It hath been an opinion,” says Lord Bacon, “that the French are wiser than they seem, while the Spaniards seem wiser than they are.” We leave it to our readers to determine whether the wasps are wiser than they seem or seem wiser than they are.