Which life stage immediately follows the larvae phase in beetles?

The life stage that immediately follows the larvae phase in beetles is the pupa stage. After the larvae, which is a feeding and growing stage, the insect undergoes significant changes as it transitions into the pupal stage. During this time, the larva undergoes metamorphosis, where it transforms into an adult beetle. The pupa stage is critical as it allows the beetle to reorganize its body structure; it does not feed during this period, and this stage can vary in duration depending on species and environmental conditions.

The options referencing the egg stage and grub stage do not represent the immediate progression from larvae, as eggs precede the larval stage in the life cycle, and "grub" is often used to describe certain larvae of specific beetle species, but it does not indicate a distinct stage following larval development across all beetles. The adult stage, while it is the final form of the beetle, comes after the pupa, making pupa the correct answer in the sequence of development stages for beetles.