Slight or no Metamorphosis
In primitive wingless insects (Apterygota) such as spring tails, silver fish etc. and in secondarily apterous insects the young ones which hatch from the egg are essentially identical to imago, differing from it only in size, immature reproductive organs and external genitalia. It moults several times leading to a gradual raise in size accompanied by the appearance of the external genitalia and maturation of sex-organs. In apterygotes, growth and moulting are seen to carry on even after reproductive maturity. Such development or life cycle is called ametabolous.
Egg -> Young goes through several stadia and moults -> Imago (Adult)
Figure: Ametabolous type of development in Lepisma