Four varieties of bacteria have been found in the bee bread of the larva: Bacillus circulans, B. coagulans, B. firmus, and B. megaterium. Only the Bacillus genus has been found in the samples taken. Together, these four species were able to hydrolyze starch, ferment glucose, convert nitrates to nitrites, and produce dihydroxyacetone from glycerol. This group of bacteria also lowers the pH of the bee bread. These functions serve not only to protect the larva from other bacteria, but they also digest complex molecules which allow the larva to easily absorb nutrients without expending a lot of energy. The bacteria, in turn, receive a supply of food which results in a mutualistic relationship.
Centris pallida is a species of solitary bee native to North America. It lacks an accepted common name; however, it has been called the digger bee, the desert bee, and the pallid bee due to its actions, habitat, and color respectively. The solitary nature of this bee allows for a dual-strategy mating system which produces an evolutionarily stable state resistant to invading strategies. These bees have also evolved to withstand the high temperatures of their native habitat. C. pallida routinely has internal temperatures within 3 degrees Celsius of death.
Male C. pallida are able detect the pheromones which females release and use them to locate female burrows. When a virgin female is about to emerge from her burrow, she releases a scent that wafts up through the soil and is detected by the antenna of the males. This has led to males developing a very acute olfactory sense. Freshly-killed females have been buried to test whether sound also plays a part in male signaling. In these tests, male bees still dug up the dead females, proving that pheromone signaling is the only pathway. Males have also been observed to dig up other males. This shows that males and virgin females give off similar pheromones. Oddly, males also sometimes dig up other digger bee species. It is currently unknown why this occurs.