THE GREAT GOLDEN DIGGER

THIS wasp (Sphex ichneumonea Linn.) is one of our most beautiful species, its great size and its brilliant color, as it flies among the flowers, serving to make it well known to all observers of nature. During the later part of July, all through August, and even in the early days of September it is commonly found at work making or storing its burrow. It is rare in our garden, however, and we thought ourselves fortunate in being able to keep track of one individual from the making to the closing of the nest. Although large and powerful it is gracefully formed. In color it is brown, varied with bright yellow.

On the morning of the third of August, at a little after ten o’clock, we saw one of these hunters start to dig a nest on the side of a stony hill. After making some progress in the work she flew off and selected a second place, where she dug so persistently that we felt confident that this was to be her final resting-place; but when the hole was two and one half inches deep, it too was deserted. Again our wasp chose a spot and began to burrow. She worked very rapidly, and at twenty minutes before twelve the hole was three inches deep. At high noon she flew away, and was gone forty minutes. The day was excessively hot, about 98° Fahr., and we ourselves were only deterred from taking a noonday rest by our fixed determination not to leave the place until we had seen all that there was to be seen in the manoeuvres of ichneumonea. On returning she appeared very much excited, fairly quivering with vitality as she resumed her work. She came up backward, carrying the earth with her mouth and anterior legs, and went back from the opening some little distance, when it was dropped, and she at once went in again. While in the burrow we could hear her humming, just as the PelopÆi do when, head downward in the wet mud, they gather their loads for nest-building. In five or six trips a little mass of earth would accumulate, and then she would lie quite flat on the heap and kick the particles away in all directions. As the work progressed the earth was carried further and further away before it was placed on the ground, and as she backed in different directions the material brought out was well spread about from the down-hill side of the nest. Sometimes she would spend several moments in smoothing the dÉbris all around, so that the opening presented much the appearance of an immense ant-hill, only the particles were much larger. During the first hour that we watched her she frequently turned directly toward us, and, sometimes remaining on the ground and sometimes rising on her wings to a level with our faces, appeared to be eyeing us intently for four or five seconds. Her attitude was comical, and she seemed to be saying, “Well, what are you hanging around here for?”

ill59

As the afternoon wore on she worked more calmly and her fidgety and excited manner disappeared, the excavation progressing steadily until half-past three. At that time she came out and walked slowly about in front of her nest and all around it. Then she rose and circled just above it, gradually widening her flight, now going further afield and now flying in and out among the plants and bushes in the immediate vicinity. The detailed survey of every little object near her nest was remarkable; and not until her tour of observation had carried her five times entirely around the spot did she appear satisfied and fly away. All her actions showed that she was studying the locality and getting her bearings before taking her departure. A fact that impressed us very much was that with the two nests that she had begun and then deserted she had taken no such precaution, but simply came up and flew off. Had she made up her mind, if we may be allowed to use the term, that the localities were in some way unsuitable and that hence she had no occasion to return to them? Had she decided, in the last instance, that she would return and so must get her bearings? We wondered how far the different acts were instinctive, or were, as Huber has it, an evidence of a “little dose of judgment.” Bates, in speaking of Monedula signata, says that he often noticed it taking a few turns about the locality of its nest, and that he was convinced that it was doing so for the purpose of getting its bearings. Belt, having described how he fed a specimen of Polistes carnifex with a caterpillar, which the wasp cut into two parts, goes on to say: “Being at the time amidst a thick mass of fine-leaved climbing plant, it proceeded, before flying away, to take note of the place where it was leaving the other half. To do this, it hovered in front of it for a few seconds, then took small circles in front of it, then larger ones around the whole plant. I thought it had gone, but it returned again, and had another look at the opening in the dense foliage down which the other half of the caterpillar lay.”[2] He then remarks that when the wasp came back for the remaining half it flew straight to its nest without taking any further note of the locality. Both of these writers believe that many of the actions of insects that are ascribed to instinct are really evidence of the possession of a certain amount of intelligence.

ill61

To return to our Sphex. When she flew away we naturally supposed that she had gone in search of her prey, and we were on the qui vive to observe every step in her actions when she came home. Alas! when she came back half an hour later, she was empty-handed. She dug for four minutes, then flew off and was gone two minutes, then returned and worked for thirty-five minutes. Another two minutes’ excursion, and then she settled down to work in good earnest and brought up load after load of earth until the shadows grew long. We noticed that on these later trips she flew directly away, depending upon her first careful study of the surroundings to find her way back. At fifteen minutes after five the patient worker came to the surface, and made a second study, this time not so detailed, of the environment. She flew this way and that, in and out among the plants, high and low, far and near, and at last, satisfied, rose in circles, higher and higher, and disappeared from view. We waited for her return with all the patience at our command, from fifteen minutes after five until fifteen minutes before seven. We felt sure that when she came back she would bring her victim with her, and when we saw her approaching we threw ourselves prone on the ground, eagerly expecting to see the end of the drama; but her search had been unsuccessful,—she carried nothing. In the realms of wasp-life, disappointments are not uncommon, and this time she had us to share her chagrin, for we felt as tired and discouraged as she perhaps did herself. When we saw her entering without any provision for her future offspring, we were at a loss what to do next; and it may be that this state of mind was shared by her also, for she at once began to fill in the entrance to her nest. We now thought it time to act, and decided to capture her, to keep her over night in one of our wasp-cages, and to try to induce her to return to her duty on the following day. We therefore secured her in a large bottle, carried her to the cottage, and having made every possible arrangement for her comfort, left her for the night.

ill63

.

On the next morning, at half after eight o’clock, we took Lady Sphex down to her home, and placed the mouth of the bottle so that when she came out she had to enter the nest. This she did, remaining below, however, only a moment. When she came up to the surface she stood still and looked about for a few seconds, and then flew away. It surprised us that having been absent from the place for so many hours, she made no study of the locality as she had done before. We thought it a very unpromising sign, and had great fears that she was deserting the place and that we should see her no more. One would need to watch a wasp through the long hours of a broiling hot day to appreciate the joy that we felt when at nine o’clock we saw her coming back. She had no difficulty in finding her nest, nor did she feel any hesitation as to what ought to be done next, but fell to work at once at carrying out more dirt. The weather, although still hot, had become cloudy and so threatening that we expected a down-pour of rain every moment, but this seemed to make no difference to her. Load after load was brought up, until, at the end of an hour, everything seemed completed to her satisfaction. She came to the entrance and flew about, now this way, and now that, repeating the locality study in the most thorough manner, and then went away. At the expiration of an hour we saw her approaching with a large light green meadow-grasshopper, which was held in the mouth and supported by the fore legs, which were folded under. On arriving, the prey was placed, head first, near the entrance, while the wasp went in, probably to reassure herself that all was right. Soon she appeared at the door of the nest and remained motionless for some moments, gazing intently at her treasure. Then seizing it (we thought by an antenna) she dragged it head first into the tunnel.

The laying of the egg did not detain her long. She was up in a moment and began at once to throw earth into the nest. After a little she went in herself, and we could plainly hear her humming as she pushed the loose material down with her head. When she resumed the work outside we interrupted her to catch a little fly that we had already driven off several times just as it was about to enter the nest. The Sphex was disturbed and flew away, and this gave us an opportunity to open the burrow. The grasshopper was placed on its back, with its head next to the blind end of the pocket and the legs protruding up into the tunnel.

We found that the egg of the wasp, which was seven millimeters long, and rather slender, was placed on the under face of the thorax at a right angle to its length, and parallel with the femur of the second leg. This leg had apparently been stung so that it had swollen and folded over the free end of the egg, which was thus firmly held in place at both extremities.[3] Upon examination we found that the abdomen of the grasshopper was beating regularly and automatically, but the closest observation failed to discover any other movements, nor would any part respond when stimulated. At three o’clock in the afternoon we found the abdomen still pulsating, and, in addition, that both antennÆ moved several times when we lifted off the cover of the jar that contained the insect. On the next morning the grasshopper was very lively, the antennÆ and labial palpi moving without stimulation. It had passed fÆces, and was able to lift its abdomen, which was curved over toward the head, as it lay on its back, frequently and with considerable violence. On the next afternoon there was no change in the movements, but the egg was dead. On the seventh the grasshopper responded to stimulation by a slight movement of the palpi and the end of the abdomen. The pulsation of the abdomen continued until the afternoon of the eighth, when it ceased, no effort of ours succeeding in starting it again. The movements of the antennÆ and palpi grew weaker and weaker on the ninth, and on the morning of the tenth the insect was dead, a period of five and a half days having elapsed since it was brought into the nest.

We had not supposed that the digging up of her nest would much disturb our Sphex, since her connection with it was so nearly at an end; but in this we were mistaken. When we returned to the garden about half an hour after we had done the deed, we heard her loud and anxious humming from a distance. She was searching far and near for her treasure house, returning every few minutes to the right spot, although the upturned earth had entirely changed its appearance. She seemed unable to believe her eyes, and her persistent refusal to accept the fact that her nest had been destroyed was pathetic. She lingered about the garden all through the day, and made so many visits to us, getting under our umbrellas and thrusting her tremendous personality into our very faces, that we wondered if she were trying to question us as to the whereabouts of her property. Later we learned that we had wronged her more deeply than we knew. Had we not interfered she would have excavated several cells to the side of the main tunnel, storing a grasshopper in each. Who knows but perhaps our Golden Digger, standing among the ruins of her home, or peering under our umbrella, said to herself: “Men are poor things: I don’t know why the world thinks so much of them .”

Dr. Packard describes Sphex ichneumonea as nesting in gravelly walks, where it digs to a depth of from four to six inches, using its jaws and fore legs to do the excavating. While the wasps that he observed completed the hole in half an hour, ours was actually at work a little over four hours. Her nest, as is shown in the drawing, measured seven and one half inches to the beginning of the pocket, which was three quarters of an inch wide by one and one half inches long. The yellow-winged Sphex, a native of France, was found by Fabre to take several hours to make her nest, working in hard ground; while another species, also studied by this observer, dug in soft earth, either in the ground or in the accumulations on the roofs of buildings, and completed her work in fifteen minutes at the most. These variations in the habits of closely related species should be carefully studied in any attempt toward an explanation of their instincts.

Fabre’s account of the genus Sphex, as it appears in France, is most interesting. He says that the yellow-winged species, living in colonies, first digs her nest and then secures her cricket, which is brought, on the wing, to the neighborhood of the burrow, the last part of the journey being accomplished on foot. The cricket is dragged by one of the antennÆ, and is not left until the nest is reached. It is then placed so that the antennÆ reach precisely to the opening, and there it is left while the wasp descends hurriedly into the depths of the burrow. In a few seconds she reappears, showing her head outside, seizes the antennÆ of the cricket, and drags it below. These manoeuvres are repeated with a striking degree of invariability.

The other Sphex first secures her prey, which is too large and heavy to be carried far, and then digs her nest in the neighborhood of the capture. This being done, she returns to her victim, and straddling it drags it by one or both of the antennÆ. Sometimes the whole journey is accomplished at once, but oftener the wasp suddenly drops her burden and runs rapidly to her nest. Perhaps it seems to her that the entrance is not large enough to accommodate a creature of such size; perhaps she imagines some imperfections of detail which would impede the process of storing it up. The work is retouched, the doorway enlarged, the threshold smoothed. Then she returns to her booty and again starts with it. After a few steps the Sphex seems to be seized with another idea. She has visited the doorway, but has not seen the interior. Who knows whether all is well within? She drops her prey and again runs off. The visit to the interior is made, more touches are given, and once more she returns. Will the journey be accomplished this time? Impossible to say. Some wasps, more given to worry than others or more forgetful of the small details of architecture, to repair their neglect or to clear up their suspicions, abandon their booty five or six times in succession to retouch the nest or simply to visit the interior. The prey, once brought to the nest, is carried in without the preliminaries that are common to the other species.