The western flower thrips (Frankliniella occidentalis) develops in six stages: egg, two larval instars, prepupa, pupa, and finally the adult insect. The eggs of the western flower thrips (Frankliniella occidentalis) are laid in leaves, flower petals and in the soft parts of stalks. They are inserted into the plant tissue with a saw-like ovipositor.
Larvae are nearly transparent white or yellowish to orange-yellow, with a large head and bright red eyes. Adult females are very variable in colour. They range from almost white through yellowish orange to almost black.
Western flower thrips (Frankliniella occidentalis) usually pupate in the ground, although pupae can also be found on leaves, in flowers or in other sheltered places. The prepupal and pupal instars can be recognized by their developing wing buds. Compared to the prepupa, the pupa has longer, more developed wing buds and longer antennae that are curved back over the head. The prepupal and pupal instars do not feed and only move if disturbed. In the adults both pairs of wings are fully developed.