When do the immature stages of Anthidium manicatum overwinter?

The entire immature stage, encompassing both the larva and the pupa, spends the winter inside the sealed brood cells.

The life cycle timing for the Wool Carder Bee includes a critical overwintering phase that occurs entirely within the confines of the nest. After the female provisions the individual brood cells and seals them with plant fluff, the laid egg hatches into a larva. This larva consumes the provisions and develops through the pupal stage, all while remaining protected inside the sealed cell. This entire immature duration—larva and pupa—persists through the colder months, meaning the species is not actively seen during winter. The emergence of the new generation of adult bees occurs the following spring or early summer, restarting the active annual cycle.