Western flower thrips is about 1 mm long, with the female larger than the male. The female varies from yellow to dark brown, and has a more rounded abdomen. The male is always pale yellow and has a narrower abdomen. Yellowish eggs cannot be seen because they are laid into the plant tissue. The larvae develop through two instars and are distinctly yellow.
Second instars become whitish prior to molting.
Both prepupa and pupa are yellowish, quiescent non-feeding stages. The antennae and wing pads are typical for most thrips species. The distribution was thought to be limited to west of the Mississippi River prior to 1980. However, this thrips has become the most prevalent species attacking greenhouse flowers throughout the United States and Canada, and many countries in Europe and Asia. This thrips feeds on almost any flowering plant.