Whiteflies all feed on phloem sap. Immature and adult stages all possess a specialized structure around the anus concerned with safe disposal of sugary honeydew, consisting of a depression (the vasiform orifice) and a hinged lingula; this is only found in the Aleyrodoidea. The adult has two pairs of wings of subequal size, dusted with powdery wax (usually white). The hind legs are not strongly adapted for jumping but adults fly very readily and are the main dispersive stage; tarsi are each two-segmented, with a double terminal claw. Reproduction is usually sexual; pedunculate eggs are laid on leaf undersides, sometimes with the peduncle inserted in a stoma; there are four immature stages, the last three of which are completely sessile; late immature stages of some species secrete elaborate wax coverings.