A type of growth or life cycle in insects in which there is slight or no metamorphosis, only a gradual increase in size.
An example of ametabolous insect is the silverfish Lepisma in which there is almost no change in form but only in size throughout its life cycle.
Word origin: a- prefix meaning "without" or "not" + Gk metabol(e) change + -ism.
Compare: holometabolism, hemimetabolism.
See also: metamorphosis.