Western flower thrips eggs are delicate, cylindrical, slightly kidney shaped, smooth and translucent white. First stage larvae are very tiny, almost worm-like insects that are translucent white. Second stage larvae are also translucent white, but are similar to the adult in size and shape. Both instars have red eyes. Prepupae are similar to second stage larvae except that the wing buds are externally visible.
Pupae have longer wing buds and the antennae are folded back over the head.
Biology A few years ago, the western flower thrips occurred only in the western United States and Canada. It is apparently now a widespread floricultural pest across North America and parts of Europe. The western flower thrips transmits tomato spotted wilt virus and impatiens necrotic spot virus. During the past several years, tomato spotted wilt virus has caused severe damage to tomato, tobacco, and peanut crops along the Gulf Coast states and Tennessee and Kentucky. Greenhouse losses due to impatiens necrotic spot virus have been severe.