They look like flat white scales with small yellowish to reddish areas near the center. It has three pairs of true legs on the thorax and five pairs of fleshy prolegs on the abdomen. Larvae are about inch long when fully grown. Once larvae are fully grown, they drop to the ground and spin a hibernation chamber where they overwinter. There is only one generation per year.
Young larvae move to the stem end of the fruit, enter, and feed on the flesh.
A single larva may feed on many as eight berries to complete its development. They move from one berry to another within a cluster and usually web the berries together with silk. The inner flesh of developing and ripening berries is consumed entirely by fruitworm larvae. The frass of the larvae fills the tunnels in the berries cling to the silk webbing, producing very messy feeding sites, which easily distinguish cranberry fruit worm damage from cherry fruitworm damage. This method is still practical in small plantings with light infestations.