What was lacking to this egg, that it should fail to produce a grub?
Perhaps a bath of sunlight; the incubating heat of which the outer egg has robbed it.
Whether on account of the fact that it is shadowed by the other egg, or for other reasons, the elder of the eggs in a group of two rarely follows the normal course, but perishes on the pod, dead without having lived.
There are exceptions to this premature end; sometimes the two eggs develop equally well; but such cases are exceptional, so that the Bruchid family would be reduced to about half its dimensions if the binary system were the rule.

To the detriment of our peas and to the advantage of the beetle, the eggs are commonly laid one by one and in isolation.
A recent emergence is shown by a little sinuous ribbon-like mark, pale or whitish, where the skin of the pod is raised and withered, which starts from the egg and is the work of the new-born larva; a sub-epidermic tunnel along which the grub works its way, while seeking a point from which it can escape into a pea.

This point once attained, the larva, which is scarcely a twenty-fifth of an inch in length, and is white with a black head, perforates the envelope and plunges into the capacious hollow of the pod.
It has reached the peas and crawls upon the nearest.

I have observed it with the magnifier.

Having explored the green globe, its new world, it begins to sink a well perpendicularly into the sphere.