The Life and Love of the Insect

by Jean-Henri Fabre

The provisions, therefore, even though they have to last but three or four weeks, are exposed to the risk of drying up before that time and becoming uneatable. When, instead of the tender bread of the start, the unhappy worm finds no food for its teeth but a repulsive crust, hard as a pebble and unassailable, it is bound to perish of hunger. And it does, in fact, so perish. I have found numbers of these victims of the August sun who, after eating plentifully of the fresh victuals and digging themselves a cell, had succumbed, unable to continue biting into fare too hard for their teeth. There remained a thick shell, a sort of closed oven, in which the poor wight lay baked and shrivelled up.

While the worm dies of hunger in the shell turned to stone by desiccation, the full-grown insect that has finished its transformations dies there too, for it is incapable of bursting the enclosure and freeing itself. I shall return later to the final delivery and will linger no more on this point. Let us occupy ourselves solely with the woes of the worm.

The drying-up of the victuals is, we say, fatal to it. This is proved by the grubs found baked in their oven; it is also proved, in a more precise fashion, by the following experiment. In July, the period of active nidification, I place in wooden or cardboard boxes a dozen pears dug up, that morning, from the native spot. These [[27]]boxes, carefully closed, are put away in the dark, in my study, where the same temperature reigns as outside. Well, in none of them is the infant reared: sometimes the egg shrivels; sometimes the worm is hatched, but very soon dies. On the other hand, in tin boxes or glass receptacles, things go very well: not one attempt at rearing fails.

Whence do these differences arise? Simply from this: in the high temperature of July, evaporation proceeds apace under the pervious wooden or cardboard screen; the alimentary pear dries up and the poor worm dies of hunger. In the impermeable tin boxes, in the carefully-sealed glass receptacles, evaporation does not take place, the provisions retain their softness and the grubs thrive as well as in their native burrow.

The insect employs two methods to ward off the danger of desiccation. In the first place, it compresses the outer layer with all the strength of its wide armlets, turning it into a protecting rind more homogeneous and more compact than the central mass. If I smash one of these well-dried boxes of preserves, the rind usually breaks off sharp and leaves the kernel in the middle bare. The whole suggests the shell and the almond of a filbert. The pressure exercised by the mother when manipulating her pear has influenced the surface layer to a depth of a few millimetres and from this results the rind; further down, the pressure has not spread, whence proceeds the central kernel. In the hot summer months, my housekeeper puts her bread into a closed pan, to keep it fresh. This is what the insect does, in its fashion: by dint of compression, it confines the bread of the family in a pan.

The Sacred Beetle goes further still: she becomes a geometrician capable of solving a fine problem of minimum [[28]]values. All other conditions remaining equal, the evaporation is obviously in proportion to the extent of the evaporating surface. The alimentary mass must therefore be given the smallest possible surface, in order by so much to decrease the waste of moisture; nevertheless, this smallest surface must unite the largest aggregate of nutritive materials, so that the worm may find sufficient nourishment. Now which is the form that encloses the greatest bulk within the smallest superficial area? Geometry answers, the sphere.

The Scarab, therefore, shapes the worm’s allowance into a sphere (we will pass over the neck of the pear for the moment); and this round form is not the result of blind mechanical conditions, imposing an inevitable shape upon the workman; it is not the forcible effect of a rolling along the ground. We have already seen that, with the object of easier and swifter transit, the insect kneads the plunder which it intends to consume at a distance into an exact ball, without moving it from the spot at which it lies; in a word, we have observed that the round form precedes the rolling.

In the same way, it will be shown presently that the pear destined for the worm is fashioned down in the burrow. It undergoes no process of rolling, it is not even moved. The Scarab gives it the requisite outline exactly as a modelling artist would do, shaping his clay under the pressure of the thumb.

Supplied with the tools which it possesses, the insect would be capable of obtaining other forms of a less dainty curve than its pear-shaped work. It could, for instance, make the coarse cylinder, the sausage in use among the Geotrupes; simplifying the work to the utmost, it could leave the morsel without any settled form, just as it [[29]]happened to find it. Things would proceed all the faster and would leave more time for playing in the sun. But no: the Scarab adopts exclusively the sphere, so difficult in its precision; she acts as though she knew the laws of evaporation and geometry from A to Z.

It remains for us to examine the neck of the pear. What can be its object, its use? The reply forces itself upon us irresistibly. This neck contains the egg, in the hatching-chamber. Now every germ, whether of plant or animal, needs air, the primary stimulus of life. To admit that vivifying combustible, the air, the shell of a bird’s egg is riddled with an endless number of pores. The pear of the Sacred Beetle may be compared with the egg of the hen. Its shell is the rind, hardened by pressure, with a view to avoiding untimely desiccation; its nutritive mass, its meat, its yolk is the soft ball sheltered under the rind; its air-chamber is the terminal space, the cavity in the neck, where the air envelopes the germ on every side. Where would that germ be better off, for breathing, than in its hatching-chamber projecting into the atmosphere and giving free play to the interchange of gases through its thin and easily penetrable wall and especially through the felt of scrapings that finishes the nipple?