The greenhouse whitefly (Trialeurodes vaporariorum) goes through six stages, namely egg, first, second, third and fourth larval stage (often referred to as ‘pupa’ although strictly spoken this is not true) and adult. The larvae are found on the underside of young leaves and have an oval shape. The first instar larvae (crawlers) are mobile, whereas the rest of the larvae stadia remain flattened on the leaf. The fourth larva stadium develops into a white, oval case encircled by a ring of erect waxy rods. This is called the pupa stadium and these pupae are found on the oldest leaves.
The adult emerges from the pupa via a T-shaped fissure. The adult whiteflies can usually be found in the top of the plant and on the underside of young leaves, where they deposit their eggs. When shaking infested plants, adults will first fly, then return to the underside of the leaves. The adult greenhouse whitefly (Trialeurodes vaporariorum) has well-developed piercing-sucking mouthparts and begins to feed on plant sap very soon after emerging. The insect is covered with a white waxy substance.