Hitting Rock Bottom: The Strange Burrowing Habits of Sandstone-excavating Bees
Entomologists from the Utah State University have observed the bees in the American Southwest desert, a harsh environment where the bees had been nesting in sandstone for almost 40 years at two sites in the San Rafael Desert. Publishing the study in Current Biology, Michael Orr, a Utah State University doctoral student in biology and the lead author of the paper, was impressed by the bees' determination to build in such a hostile place. "Not much is known about this hard-to-find species and our first step was to confirm it actually prefers nesting in sandstone. Once we confirmed this preference, the next step was to explore why the bees expend such tremendous effort and energy, limiting their ability to reproduce, to create these shelters."
Another of the study's authors, retired United States Department of Agriculture - Agricultural Research Service research entomologist Frank Parker, was the one who had originally discovered the bees four decades ago. He had collected samples of the nests and reared the inhabitants to emergence, but it was only in recent years that he had collaborated with Orr to unearth five new nesting sites ranging from Ancestral Puebloan sandstone cliff dwellings at Colorado's Mesa Verde and natural formations in southern Utah and California's Death Valley.
"These bees are considered uncommon as the bees use water to help excavate sandstone, we found many sites by targeting areas near water." shared Orr. "Sandstone is more durable than most other nesting options and any bees that do not emerge from these nests in a year are better protected. Delayed emergence is a bet-hedging strategy for avoiding years with poor floral resources, especially useful in the drought-prone desert."
In addition to the tough, elevated shelters protecting the bees from erosion and sudden flash floods, they also help to control parasite build-up across years and may even deter growth of threatening microbes. "The desert is a hard place to live," Orr concluded. "Anthophora pueblo has pioneered a suitable niche between a rock and a hard place."