Some mayflies have 20-45 molts. More advanced insects tend to go through 4-6 molts. Adults result from progressive development. The newly hatched larvae are small and lack genitalia. At each molt they get larger, and genitalia get more complete.
Adults are obviously wingless.
Newly hatched young are very similar in shape to the adults, but lack genitalia, wings and maybe adult type of cuticle. Most insects gradually acquire adult features. Later instars will have wing pads where the wings are developing. Genitalia also develop progressively. This type of development occurs in the Ephemeroptera, Odonata, Plecoptera, and the young of these insects are sometimes called naiads.