Spring brings the Digger Bees (Genus Anthophora ) out of the ground as they emerge from the nests prepared by female bees the year before. One of the Diggers with the largest, most active aggregations in Mount Diablo State Park is the Edwards Digger Bee, and they begin to emerge in late February and early March. The males emerge first and begin noisily patrolling the nesting areas (often a wide fire trail, such as Old Finley Road or Burma Road). The females emerge next and, after mating, begin to dig tunnels. 

A female will construct a single nest cell at the end of this tunnel, about 3-4 inches down, and fill it with a nectar-pollen mixture, upon which they lay a single egg. She then seals the nest and gets to work on another one. Her larva will feed on the nest provisions and pupate in the fall. Adults hatch in the fall, but stay underground until the following February/March.

Alas, it doesn’t always go smoothly for the Edwards Digger Bee. In addition to parasitic threats posed by Bee Flies (Family Bombyliidae), Miltogrammine Flies (Subfamily Miltogramminae, Family Sarcophagidae), Cuckoo Wasps (Family Chrysididae) and other insects, there may be a Lovely-Tailed Mourning Bee (Melecta separata callura) lurking nearby. 

The Lovely-Tailed Mourning Bee is a medium-large, strikingly beautiful bee, but with a life history that is adversarial to that of Anthophora Digger Bees. It will seek out a completed nest, dig it out, and lay her own egg in the nest cell. Its larva will hatch first and will eat the egg of the host bee and any other parasite eggs, and eat the pollen contents of the nest. The larva then pupates in the nest cell, and will emerge the following year.