Larvae and adults of these insects are very different and a distinct pupae is formed. In these insects, the nymph more or less resembles the adult and there is no pupal stage. The example shown below is a plant bug.
Ametabolous insects show no metamorphosis.
Here the adult looks like the immature except for the presence of genetalia and gonads. The silverfish is an example. Once an insect becomes an adult it will not grow. To grow and become an adult, young insects shed or molt their exoskeleton. Molting happens several times before an insect becomes an adult.