The Wild World of Native Bees: Nesting Habits You Never Knew

Field report

From petal-lined cradles to tunnels carved in clay, the nesting ingenuity of wild bees is astonishing.

Wildlife Correspondent has covered native pollinators and insect ecology for outlets including National Geographic, The Guardian, and Audubon Magazine.

Entomology Archives / American Museum of Natural History

Back in 2009, in a coincidence that was clearly instigated by flower fairies, two separate teams of scientists stumbled upon the exquisite handiwork of Osmia avosetta bees. The discoveries were a single day apart; one team in Turkey, the other in Iran.

And why are we writing about this now, so many years later? Because what they discovered are some of the prettiest things we've ever seen: Wee nests intricately crafted from flower petals, each one taking a day or two to build to offer a safe haven for a single bee egg.

Researchers now reveal that pesticides, in fact, travel far and wide after initial agricultural application, leaching into aquifers, rivers, oceans, and soils.

The global study analyzed the geographic distribution of 92 of the most commonly used agricultural pesticides and found that approximately 70,000 tonnes (77,000 U.S. tons or 155 million pounds) of potentially harmful chemicals leach into aquifers each year, impacting ecosystems and freshwater resources.

To perform this beautiful task, mother bees bite off the petal from the flower and fly it back, one by one, to the nest site. She starts the nest in a small burrow, layering petals in a surprisingly orderly fashion. As described in the research, which was published in the AMNH publication, American Museum Novitates:

"...the petals were all shaped like the upper part of a heart and were arranged in the same manner: their tips pointed downward and the cut side pointed upward and they overlap like scales in both the inner and the outer petal linings."

“This degradation of pesticides often occurs as a ‘cascade’ of molecules into the surrounding environment, which can persist in the environment for a long time and can be just as harmful as the parent molecule or applied pesticide. One such example is glyphosate. Although it is highly degradable, it breaks down into a molecule known as AMPA that is both highly persistent and toxic,” says Maggi.

The study reveals that only a fraction of pesticides enter river systems. But once they are in the water, most of the active ingredients end up in the ocean. This puts at risk the very basis of marine and freshwater food chains," the authors explain, with potential negative impacts on marine wildlife and coral reefs.

Entomology Archives / American Museum of Natural History

Dr. Federico Maggi, Dr Francesco Tabiella, Dr Fiona Tang

Details of the flower nests reveal the delicate attention to layering and the remarkable precision of each petal placement.

“Just because we don’t see pesticide residues in soil and water doesn’t mean they’re not there, impacting critical systems on land, rivers and oceans," says paper co-author Dr. Fiona Tang from Monash University.

Remarkably, the authors say that the numbers are conservative because not all pesticides were included in the analysis. Legacy pesticides, those used in aquaculture, private dwellings, and public spaces, were not included—meaning the risk of these chemicals to ecosystems and people is likely higher.

Entomology Archives / American Museum of Natural History

We should all be so lucky as to have petalled walls surrounding us. But aside from their beauty, the flowery nests are purpose-built. The researchers explain that the floral shell includes trapped air that would allow it to float were the area flooded. As well, the moisture of the petals helps maintain the water content of the nest and provisions. Meanwhile, the rigidity of the nest protects its inhabitant from predators and parasites. As the study notes:

"Although the patchwork of colors on the outer surface of a cell or even the strong colors is a striking phenomenon to the human eye, color of the cell surface is obviously not important to the female bee or her nest. We think the survival value of constructing this elaborate cell lining of petals and soil is the texture, water content, and water repellent–and humidity-retaining nature of petals."

"It is important that national authorities disclose statistics on the use of agricultural inputs, be they fertilizers or pesticides, given the effect they have on the environment and ecosystem service."

The study, "Agricultural pesticide land budget and river discharge to oceans," was published in Nature.

Entomology Archives / American Museum of Natural History