Lady beetles are easily recognized by their shiny, convex, half-dome shape and short, clubbed antennae. Most lady beetles, including this species, are predaceous as both larvae and adults. Young lady beetle larvae usually pierce and suck the contents from their prey. Older larvae and adults chew and consume their entire prey. Larvae are active, elongate, have long legs, and resemble tiny alligators. Many lady beetles look alike and accurate identification requires a specialist.
Unless disrupted by pesticide use or other adverse conditions, the vedalia beetle and the parasitic wasp, Cryptochaetum iceryae, provide complete biological control of the cottony cushion scale. R. cardinalis was introduced into California citrus groves in 1888 and saved the citrus industry from destruction by the cottony cushion scale. Due to its success, the vedalia's introduction is now viewed as the beginning of classical biological control.
Adult vedalia beetles are small, measuring 2-4 mm (<3/16 inch) long, and are red and black with a covering of fine hairs which often gives them a grayish appearance. The larvae are reddish in color. Red and black pupae develop within the grayish skin of the last larval instar and occur among or near scale colonies. Oblong, red eggs are laid singly or in groups on or near cottony cushion scales. R. cardinalis undergoes complete metamorphosis and has 8 or more generations per year. Both adults and larvae feed exclusively the cottony cushion scale on a variety of plants including rose, acacia, magnolia, olive, and citrus. Adults and mature larvae feed on all stages of the scale while young larvae feed only on eggs. The vedalia beetle is extremely sensitive to some pesticides and care should be used when applying pesticides in areas where the beetle is relied upon for control of the cottony cushion scale.