The first instar is called a crawler . It is active and moves around the plant to search for a feeding spot. Crawlers can be transferred on feet of birds. Scales are mostly sessile and are covered with a waxy secretion which is separate from the body of the insect. Females lay eggs or give birth to young under the scale.
Males have a last instar quiescent stage like a pupa but the wings develop externally.
Some produce products used by man. Chinese wax scales secretes copious amounts of wax which is used for candles. Indian wax scale wax is used for medicinal purposes. Lac insects are on fig banyan or other plants. The females exudes the lac or wax .