I have watched the Sacred Beetle at work in her den, so I know how she makes her pear-shaped nest.
With the building-materials she has collected she shuts herself up underground so as to give her whole attention to the business in hand. The materials may be obtained in two ways. As a rule, under natural conditions, she kneads a ball in the usual way and rolls it to a favourable spot. As it rolls along it hardens a little on the surface and gathers a slight crust of earth and tiny grains of sand, which is useful later on. Now and then, however, the Beetle finds a suitable place for her burrow quite close to the spot where she collects her building-materials, and in that case she simply bundles armfuls of stuff into the hole. The result is most striking. One day I see a shapeless lump disappear into the burrow. Next day, or the day after, I visit the Beetle’s workshop and find the artist in front of her work. The [[20]]formless mass of scrapings has become a pear, perfect in outline and exquisitely finished.
The part that rests on the floor of the burrow is crusted over with particles of sand, while the rest is polished like glass. This shows that the Beetle has not rolled the pear round and round, but has shaped it where it lies. She has modelled it with little taps of her broad feet, just as she models her ball in the daylight.
By making an artificial burrow for the mother Beetle in my own workshop, with the help of a glass jar full of earth, and a peep-hole through which I can observe operations, I have been able to see the work in its various stages.
The Beetle first makes a complete ball. Then she starts the neck of the pear by making a ring round the ball and applying pressure, till the ring becomes a groove. In this way a blunt projection is pushed out at one side of the ball. In the centre of this projection she employs further pressure to form a sort of crater or hollow, with a swollen rim; and gradually the hollow is made deeper and the swollen rim thinner and thinner, till a sack is formed. In this sack, which is polished and glazed inside, the egg is laid. The opening of the sack, or extreme end of the pear, is then closed with a plug of stringy fibres.
There is a reason for this rough plug—a most curious [[21]]exception, when nothing else has escaped the heavy blows of the insect’s leg. The end of the egg rests against it, and, if the stopper were pressed down and driven in, the infant grub might suffer. So the Beetle stops the hole without ramming down the stopper.