Which shouldn’t feel so alien to us because human childhoods are a period of much slower growth than you see in other animals. Not a pause but still. IIRC it’s speculated that slowed growth is to give time for the brain to mature and to learn but either way it’s interesting to think about. If we grew the way dogs and cows to we’d be fully grown by around 10 years old.
Vertebrates go through several stages in their development while in the egg (or placental sack, which stands in for the egg). The develop a head, spine, and tail initially. Then they add front limbs and finally rear limbs. Frogs hatch from their eggs prior to the limb development stage and retain that neotenous legless form while tadpoles. They are essentially hatched as embryos and don’t assume their adult form until later.
The possession of wings in the later stage created a very different environmental situation, so the selective pressures on the winged stage are very different from those in the pre winged stage. These cause a split in the evolutionary environment of pre and post winged stages, causing selection for further divergent trait acquisition in the transitional stage during wing development.
Not an entomologist though, so if anyone has a better understanding I’d be grateful.