Osmia avosetta: these solitary bees place their eggs in colorful nesting capsules that they build using flower petals, nectar, and mud
Osmia avosetta is a very rare species of mason bee that was just discovered about 16 years ago. These are solitary bees, meaning that they don't form colonies or live together in hives; each female builds her own nest instead, placing her eggs in a small batch of enclosed brood capsules and then burying the capsules in burrows and other cavities.
Each capsule contains a single egg, along with enough pollen and nectar to sustain the larva until it reaches adulthood.
Above: the photo at the top shows a capsule that was made by Osmia avosetta, and the image at the bottom shows several capsules buried in the ground at a nesting site in Turkey
Osmia avosetta builds its nesting capsules with petals from the flowers Onobrychis vicilifolia or Hedysarum elymaiticum (depending on the region). The bee uses its mandibles to trim the petals and then carries each of the pieces back to its nesting site, where the petals are carefully folded together and then formed into several small, rounded capsules. Nectar and mud are both used to "glue" the petals together.
As this article describes:
Both practical and beautiful, the mother bee first sources the perfect petals and brings them back to her nest site. She then digs a 1.5 cm-deep burrow and lays down multiple layers of overlapping petals and mud. After filling the nest with nutritious pollen and nectar, she then lays her precious egg on top. Finally, she seals the cell by folding the scale-like petals inwards and plugging the hole with mud. While the exterior drys like a hard shell, the interior stays humid, allowing a cozy environment for the larvae to grow and mature as they wait out the winter.
Above: the inside of a nesting capsule, with a tiny egg resting atop a glob of pollen and nectar
The finished capsules are a colorful, delicate patchwork of pink, purple, blue, and yellow flower petals.
This species was first discovered and described in 2009. Two separate research teams in two different countries actually discovered the species on the very same day; one team discovered it at a site in Turkey while the other discovered it in Iran, and the two teams then published their findings together in a single paper.
Above: more capsules from the nesting site in Turkey
Osmia avosetta has scarcely been documented in the 16 years that have passed since its discovery, and the research that has been published on this species primarily focuses on the nesting behavior. There are very few photos of the actual bees themselves.
Above: Osmia bee from Turkey
The photos of the nesting capsules are pretty stunning, though.
There are several other mason bees that use flower petals and/or leaves to line their nests, and bees of the family Megachilidae are also known to engage in a similar behavior, as I explained in my previous post about petalcutter and leafcutter bees.
My Modern Met: Rare Bee Species Makes Colorful Nests from Flower Petals
NPR: Busy Bees Use Flower Petals for Nest Wallpaper
American Museum Novitates: Nests, Petal Usage, Floral Preferences, and Immatures of Osmia avosetta, Including Biological Comparisons with Other Osmiine Bees
Acta Scientific Agriculture: Nature's Architects: Exploring the Biology, Behavior, and Pollination Impact of Mason Bees
