Let us try to devise something better. In a dimly-lit corner of my study I hang perpendicularly a glass tube of smaller calibre than the first. I leave it as it is, unprovided with an opaque sheath. At the bottom is a nine-inch column of earth. All the rest is empty and may be easily observed, if the Minotaurs consent to work under such disadvantageous conditions. Provided that the experiment be not unduly prolonged, they do consent and very readily, so imperious is the need of a burrow as laying-time draws nigh.
I extract from the soil a couple engaged in excavating their natural shaft and place them in the glass tube. Next morning I find them continuing their interrupted business [[108]]in broad daylight. Seated a little way off, in the shadow of the corner in which the apparatus hangs, I watch the operation, amazed by what I see. The mother digs. The father, at some distance, waits until the heap of rubbish is beginning to hamper the worker’s movements. Then he approaches. By small armfuls he draws towards him and slips beneath his abdomen the shifted earth, which, being plastic, forms into a ball under the pressure of the hind-legs.
The Beetle now turns about beneath the load. With the trident driven into the bundle, as a pitchfork is driven into a truss of hay, before tossing it into the loft, the fore-legs, with their wide, toothed shanks, gripping the load and preventing it from crumbling, he pushes with all his might. And cheerily! The thing moves and ascends, very slowly, it is true, but still it ascends! How is it done, seeing that the too smooth surface of the glass acts as an absolute check to the upward movement?
The insurmountable difficulty has been provided for. I selected a clay soil likely to leave a trace of its passage. With the cart before the horse, the load itself sands the road and makes it practicable; in rubbing [[109]]past every portion of the wall, it leaves particles of earth which constitute so many points of purchase. Therefore, as he pushes his burden upwards, the Beetle finds behind it a roughened surface which affords him a footing as he climbs.
This, after all, is all he needs, though it involves occasional slips and efforts to retain his balance, which are unknown in the natural shaft. When he comes to a certain distance from the opening, he leaves his clod, which, shaped by the tube, remains in its place, motionless. He returns to the bottom, not by allowing himself to fall suddenly, but gradually and carefully, by means of the footholds by which he made his way up. A second pellet is hoisted up and welded to the first. A third follows. At length, with a last effort, he pushes out the whole thing in a single plug.
This fractional division is a judicious method. Because of the enormous amount of friction in the narrow and uneven natural shaft, the Beetle would never succeed in hoisting the great cylinders of his mound in one lump; he carries them up in loads which are not beyond his powers and which are afterwards joined and welded together. [[110]]
I am inclined to believe that this work of assembling the component parts is performed in the slightly sloping vestibule which usually precedes the perpendicular shaft. Here no doubt the successive clods are compressed into one very heavy cylinder, which is yet easily moved along an almost horizontal road. Then the Minotaur, with a last thrust of his trident, pushes out the lump, which joins the others on the sides of the mound. They are like so many blocks of hewn stone forbidding access to the home. The rubbish thus suitably moulded provides a Cyclopean system of fortification.
In the glass tube, the climbing is such difficult work that the insect is soon discouraged. The frail footholds left by the load crumble and fall off, swept away by the tarsi vainly seeking a support; and the tube again becomes smooth over wide extents of its surface. The climber ends by giving up struggling against the impossible; he abandons his bundle and drops to the bottom. The works cease henceforth; the couple have recognized the treachery of their strange dwelling. Both of them try to get away. Their uneasiness is betrayed by continual attempts to escape. I set them free. [[111]]They have told me all that they were able to tell me in conditions so favourable to me and so bad for themselves.
To return to the large apparatus, where the work is proceeding correctly. The boring, begun in March, finishes by the middle of April. From this time onward, my daily visits no longer show me on the top of the mound a plug of fresh earth, marking a recent ejection of rubbish.
It must therefore take two or three weeks at least to excavate the dwelling. My observations in the open even lead me to think that a month or longer is not excessive. My two captives, disturbed in the midst of their earlier labours and pressed for time by the lateness of the season, cut short this work, which for that matter they were unable to continue when the cork stopper appeared at the bottom of the tube as an insuperable obstacle. The others, working in freedom, have an unlimited depth of sand at their disposal. They have plenty of leisure, if they start work in good time. Even before the end of February we see plenty of mounds. Later, these will mark the sites of shafts four or five feet deep. Such pits as these require a full month’s labour, if not more. [[112]]