HOW and WHY do moths lay their eggs in MEXICAN JUMPING BEANS if the larvae can't get out????

Answer 1

The eggs are not laid into the beans while they are beans. They are laid when the bean is flowering. The larvae does get out, eventually. One way to think about it, every buy a peach and bite into and find a worm but there was no hole in the peach. The egg was laid in the peach blossum and hatched after the peach formed.

Answer 2

I found this on the web -

the jumping behavior is clearly influenced by temperature. Perhaps this is a way to move the capsules out of the hot sun to a more concealed location, such as into a crevice or under a rock, prior to the final critical stages of metamorphosis during which the adult moth is formed. However, the larvae also exhibit their peculiar jerking behavior in the shade, suggesting that other genetic or physiological factors may be involved.

The larvae does eventually come out of something called a "circular exit door". The above paragraph explains the jumping behavior.