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What Is a Pollen Ball?
- Fluffy pollen, ready for collectionpollen image by asb from Fotolia.com
A female, native solitary bee creates a pollen ball from the pollen she gathers on her body hairs. She adds flower nectar to the pollen and rolls it into a ball. The pollen ball looks like a rounded crumb of soft cheese.
- Directly after mating with a male bee, a female solitary bee creates a "brood cell" where she will eventually lay her offspring. When she completes the underground, tube-like soil nest, the female bee forages for pollen on her host flowers.
- The female bee collects pollen onto her hind legs for transport.bumble bee flypass image by Robert Kelly from Fotolia.com
Grooming pollen from her body, the female bee packs the gathered yellow pollen particles into patches of her body hair (called "scopae") on her hind legs to transport back to her nest. As the dry pollen accumulates in the brood cell, the female adds flower nectar. The nectar moistens the pollen clump to a doughy consistency.
- When the pollen ball is moist and round enough, she lays an egg on top. She then constructs a brood cell cap by packing soil particles together in a spiral inverted dome. The cap closes off the nest to protect her offspring. She and the larvae now have enough rations to last them underground.
Types of Bees that Create Pollen Balls
- The bees that create pollen balls lack the social structure of honey bees or carpenter bees, according to Professor Emeritus Robbin W. Thorp, University of California, Davis, Department of Entomology. Female bees that specialize in collecting pollen from one or a few closely related species of flowering plants are called "oligoleges" (oligo = few; legere = to gather).
These solitary oligolectic bees--such as the alfalfa leafcutting bee--require pollen from their floral hosts to provide protein for development of their offspring. Life cycles of these bees are closely synchronized with the life cycle of the pollen host flowers.
More Pollen Balls
- After one successful pollen ball and larvae, the female bee digs another lateral tunnel. She then pushes the soil into the tunnel leading to the most recently completed brood cell to connect her to her offspring's pollen ball nest. According the Vernal Pools website, the system of tunnels---if one could lean over the soil and see underground---looks like a bicycle wheel, a series of spokes radiating out from the vertical entrance shaft. Each spoke ends---like a cul-de-sac---in a single brood cell with a pollen ball, and a clear, larvae-worm on top.
Interesting Maternal Fact
- Most female insects churn out hundred of eggs in a lifetime. But solitary oligolectic bees may lay only 20 to 30 eggs in their lifetimes. Most of their life's work concerns providing a secure home with a mass of food provisions adequate for their young's development. Because these maternal inserts live only one year, populations of these bees---and pollen ball creation-- recover extremely slowly from catastrophic losses.