What Do Females of Centris pallida Do to Reproduce?

A digging female digger bee.

Digging females of Centris pallida tunnel down through sandy to gravelly soil for about a foot or so before finishing off the burrow with an inch-long vertical, terminal cell located roughly eight inches beneath the surface of the soil. In this cell, the female forms a brood pot lined with wax that she then fills with nectar and pollen.  On top of the sticky mass of food, she lays an egg, which hatches into a tiny grub that feasts on the provisions provided by its mother.

A brood pot.

Once the food is gone and the grub’s development is complete, the baby bee turns itself into a pale grub-like prepupa, which rests quietly underground for 11 months or so.  Long after its mother prepared the cell for its offspring, the prepupa eventually metamorphoses into a pupa, which in turn soon becomes an adult bee. The fresh adult digs its way up to the surface and begins a very active life beginning in April or early May that runs its course in about a month or so.

As the baby bee matures, it turns into a pale grub-like prepupa. The above images show the baby bee as a larva (1), a small prepupa (2), and a larger prepupa (3). The egg hatches into a larva that gets bigger as it eats until it has finished the food in the brood pot. At that point, it stops growing and changes into a prepupa. If the larva has only had a small amount of food to eat, it will form a small prepupa; if it has eaten tons, it will become a large prepupa. But prepupae do not eat anything. They wait until the next year when they change into pupae and then adults.