Which metamorphosis involves stages of egg, adult only?

The correct answer involves understanding the different types of metamorphosis that insects undergo. The term "simple metamorphosis" refers specifically to an insect development process that includes just a few stages: egg and adult. Insects that undergo simple metamorphosis develop from an egg directly into a miniature version of the adult, known as a nymph, and eventually grow into full-sized adults without the presence of distinct larval or pupal stages.

This process allows for a more straightforward development cycle, where nymphs resemble adults but may differ in size and reproductive maturity. In contrast, complete metamorphosis includes four distinct stages: egg, larva, pupa, and adult, while gradual metamorphosis features three stages: egg, nymph, and adult, where the nymph stage may undergo multiple molts but still retains a form similar to the adult. Complex metamorphosis is not a recognized term in entomology for insect development.

Understanding these definitions clarifies the correct classification of developmental stages, highlighting why simple metamorphosis is defined solely by the presence of eggs and adults, without intermediate larval or pupal forms.