The figure emphasizes the potential to increase in size during post-embryonic development, in this species from a few milligrams at hatching to nearly 2 grams. Fully hardened cuticle does not expand, so growth of the hardest parts can only take place during molts. The softer parts of insects can expand. The softer cuticle often occurs in folds that can be expanded, and sometimes the cuticle itself can be stretched. Another figure indicates that the soft parts of an insect grow rather continuously, while the hard parts grow in steps.
Growth can refer to an increase in cell number or an increase in cell size.
The development and expression of cuticle depends on the cells of the epidermis. Epidermal cell numbers increase prior to molting in many insect species. In larvae of many Diptera, growth is due exclusively to increased size of the epidermal cells. Similarly, growth of internal organs can proceed by increased cell size or increased cell number. Both forms of growth occur in the mosquito Aedes .