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U.S. Forest Service

Centris pallida

By Zoe Statman-Weil and Vicki Wojcik, Pollinator Partnership

Big bee, little bee—the mating strategy of a solitary bee

Centris pallida is a solitary bee that can be found in the arid landscapes of the southwestern United States. Often described by observers as a ‘grey, fuzzy-looking honey bee’, C. pallida is a member of the family Apidae, so it is no surprise that it can be confused with the honey bee, Apis mellifera. 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.

There are over 110 species in the genus Centris that range in distribution as far north as the state of Kansas, all the way down to Argentina. The vast majority of the species richness in this group is found in tropical Central America, South America, and Jamaica.

Species in the genus Centris in general tend to forage orchids or flowering trees. C. Pallida in particular forages on the Palo Verde trees. The Palo Verde (Parkinsonia microphylla) is the state tree of Arizona, it symbolizes a rugged adaptation to a hot environment in which is provides beautiful yellow blooms that feed local wildlife. Palo Verde trees are unique in that they also make use of their green colored stems for photosynthesis, hence their Spanish name ‘green stick’.

Centris pallida on a flower. Centris pallida on a flower. (Photo from by Lon Brehmer and Enriqueta Flores-Guevara (Copyright 2012).

C. pallida has mostly been researched in regards to its mating patterns. The male C. pallida has two methods of mating with females: first, it waits around good food sources for the female to come forage and then it attacks. Second, the males dig up females as they emerge from their buried nests! In fact, in a scientific experiment these male bees were found to even dig up honeybees and other insects. They dig down before they know if the emerging bee is male or female, and if it is female they begin to mate in the hole they have dug. There can be up to thousands of males awaiting the females’ arrival at food sources or their emergence from burrows!

Females aren’t without a say in this system. Another scientific paper examined how female bees could determine future mating strategies of their offspring by how they construct and provision their nests. Smaller males tend to hover over food sources, waiting for females to arrive and then mate with them, while the larger males tend to dig up the virgin females. The size of a bee turns out to be directly correlated to how much food the developing larvae had. This means that food provisioning and nest building by females can determine the future behavior of their sons! Female bees can either make and provision lots of small cells in their nests, or can make fewer larger cells, thus deciding whether their sons are small or large.

C. pallida is an interesting solitary bee that can teach us a lot about varied mating patterns! If you come across a bee digging in the earth, it could very well be a male C. pallida trying to find a mate.

For More Information

  • BugGuide: Species¬†Centris pallida¬†- Pallid Bee
  • Alcock, John, C. Eugene Jones, and Stephen L. Buchmann. "Male mating strategies in the bee Centris pallida Fox (Anthophoridae: Hymenoptera)." American Naturalist (1977): 145-155.
  • Alcock, John, C. Eugene Jones, and Stephen L. Buchmann. "Location before emergence of the female bee, Centris pallida, by its male (Hymenoptera: Anthophoridae)."Journal of Zoology. 179.2 (1976): 189-199.
  • Chappell, Mark A. "Temperature regulation and energetics of the solitary bee Centris pallida during foraging and intermale mate competition." Physiological Zoology (1984): 215-225.