嗯，作者写得不严谨，是孵化，从wiki上查来：

 

Fireflies undergo a transformation called complete metamorphosis.^[14]

A few days after mating, a female lays her fertilized eggs on or just below the surface of the ground. The eggs hatch three to four weeks later, and the larvae feed until the end of the summer. The larvae are commonly called glowworms (not to be confused with the distinct beetle family Phengodidae or the fly genus Arachnocampa). Lampyrid larvae have simple eyes. The term glowworm is also used for both adults and larvae of species such as Lampyris noctiluca, the common European glowworm, in which only the nonflying adult females glow brightly and the flying males glow only weakly and intermittently.

 

A video of fireflies

Fireflies hibernate over winter during the larval stage, some species for several years.