Moreover, each grub can find its infant diet; that is, that layer which, remote from the surface, hardens only gradually and remains full of sap until a comparatively late period.  This inner layer represents the crumb of a loaf, the rest of the bean being the crust.

In the pea, a sphere of much less capacity, it occupies the central portion; a limited point at which the grub develops, and lacking which it perishes; but in the bean it lines the wide adjoining faces of the two flattened cotyledons.  No matter where the point of attack is made, the grub has only to bore straight down when it quickly reaches the softer tissues.  What is the result?  I have counted the eggs adhering to a bean-pod and the beans included in the pod, and comparing the two figures I find that there is plenty of room for the whole family at the rate of five or six dwellers in each bean.  No superfluous larvae perish of hunger when barely issued from the egg; all have their share of the ample provision; all live and prosper.  The abundance of food balances the prodigal fertility of the mother.

If the Bruchus were always to adopt the broad bean for the establishment of her family I could well understand the exuberant allowance of eggs to one pod; a rich food-stuff easily obtained evokes a large batch of eggs.  But the case of the pea perplexes me.  By what aberration does the mother abandon her children to starvation on this totally insufficient vegetable?  Why so many grubs to each pea when one pea is sufficient only for one grub?

Matters are not so arranged in the general balance-sheet of life.  A certain foresight seems to rule over the ovary so that the number of mouths is in proportion to the abundance or scarcity of the food consumed.  The Scarabaeus, the Sphex, the Necrophorus, and other insects which prepare and preserve alimentary provision for their families, are all of a narrowly limited fertility, because the balls of dung, the dead or paralysed insects, or the buried corpses of animals on which their offspring are nourished are provided only at the cost of laborious efforts.

The ordinary bluebottle, on the contrary, which lays her eggs upon butcher’s meat or carrion, lays them in enormous batches.  Trusting in the inexhaustible riches represented by the corpse, she is prodigal of offspring, and takes no account of numbers.  In other cases the provision is acquired by audacious brigandage, which exposes the newly born offspring to a thousand mortal accidents.  In such cases the mother balances the chances of destruction by an exaggerated flux of eggs.  Such is the case with the Meloides, which, stealing the goods of others under conditions of the greatest peril, are accordingly endowed with a prodigious fertility.