It abstains from other motives.
Let us remark that the peas touch laterally, and are pressed one against the other, so that the grub, when searching for a point of attack, cannot circulate at will.

Let us also note that the lower pole expands into the umbilical excrescence, which is less easy of perforation than those parts protected by the skin alone.

It is even possible that the umbilicum, whose organisation differs from that of the rest of the pea, contains a peculiar sap that is distasteful to the little grub.
Such, doubtless, is the reason why the peas exploited by the Bruchus are still able to germinate.

They are damaged, but not dead, because the invasion was conducted from the free hemisphere, a portion less vulnerable and more easy of access.

Moreover, as the pea in its entirety is too large for a single grub to consume, the consumption is limited to the portion preferred by the consumer, and this portion is not the essential portion of the pea.
With other conditions, with very much smaller or very much larger seeds, we shall observe very different results.