The colorful nesting behavior of the Osmia avosetta bees was discovered on the same day by teams in Turkey and Iran, where the insects are mostly found. The teams jointly described the behavior in the February 2010 edition of the journal American Museum Novitates.
Each bee nest has room for a single larva. The Turkish and Iranian teams also noticed regional variations between the nests: Bees in Turkey—where Rozen was working—tend to pick yellow, pink, blue, and purple petals, while Iranian bees make their nests with just purple flowers.
To learn more, the scientists watched the busy mama bees. Building a nest takes a day or two, and the female might create about 10 nests in total, often right next to each other. To begin construction, she bites the petals off of flowers and flies each petal — one by one — back to the nest, a peanut-sized burrow in the ground.
She then shapes the multi-colored petals into a cocoon-like structure, laying one petal on top of the other and occasionally using some nectar as glue. When the outer petal casing is complete, she reinforces the inside with a paper-thin layer of mud, and then another layer of petals, so both the outside and inside are wallpapered — a potpourri of purple, pink and yellow.
These meticulous shells are just over a half-inch long and usually will house just one tiny egg. To prepare for her offspring, the mother collects pollen and nectar, which she carries back to the burrow in a nifty part of the digestive tract called the crop. She deposits this gooey blob of nutritional goodness in the bottom of the flower-petal nest. Then, she lays the egg, right on top of the gelatinous blob.
To close up the nest, the bee bends the inner layers of petals toward each other, spackles the petals with mud, and folds down the outer petals for a tight seal. The casing is nearly airtight, which helps protect the vulnerable egg (and later larva, then pupa) from flooding or excessive dryness or hoofed animals. In only three to four days, the egg hatches into a larva. When it finishes feasting on the nectar, the larva spins a cocoon (still inside the shell, which has hardened into a protective casing by this point) and then hangs out. Rosen says he isn’t sure whether it spends the winter as a larva or as an adult. But at some point the creature’s tissue begins to restructure itself, and it transforms into an adult.
Come springtime, the adult bee emerges from its flowery bower.
Solitary bees generally live for about a year, but they are active for only about two months during spring and summer. The other ten months the larvae sleep underground. They don’t last for very long. They very quickly do their nesting and then they die, and then the next generation is marching on its way.
Then, the cycle starts all over again.
PHOTOS BY J.G. ROZEN, AMNH