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Native bees: Mason bees are fantastic pollinators

Photo of a blue mason bee

Mason bee (Osmia lignaria)

Mason bees might be the best pollinators of all bees. Instead of wetting pollen and putting it in pollen sacs like honeybees, mason bees are covered in hair that collects pollen as they move around, searching for nectar. They can certainly carry a lot of pollen and significant pollinators for apple, cherry and plum trees.

(Try out this nectar relay activity.)

Mason bees are in the family Megachilidae, genus Osmia and Hoplitis. There are 725 species of mason bees worldwide and about 200 in the U.S. and Canada. They can be hard to distinguish those, because mason bees can have a varied look. Some species are black, some black and yellow — looking like bumblebees, and some are bright green, like sweat bees. Most Hoplitis species are black with white stripes and are distinguished by their light green or blue eyes.

(Read about sweat bees here.)

Mason bees can also range from a tiny 4 mm to 17 mm.

However, Osmia are consistent in that they are all solitary species and nest in cavities. They will create nests in holes in standing dead trees, hollow plant stems, abandoned mud dauber wasp nests, snail shells or shallow cavities in the soil.

(Five types of wasps you might find in Iowa.)

Leafcutter bee mandible (Megachile sculpturalis)

Leafcutter bees

Also in the Megachilidae family are the Megachile, or leafcutter bees. These species have large mandibles with sharp teeth that they use to cut leaves or flower petals for nesting materials. They cut circular-shaped pieces of leaf off to cap each nest cylinder once an egg is laid and provided with pollen and nectar. A study in 2016 looked at what plants leafcutter bees used for their nests, and there was a wide variety — 54 plants species were used in the nests of three leafcutter bee species. All but six of the 54 plant leaves had microbial properties.

Photo of a wool carder bee

Wool carder bee (Anthidium oblongatum)

Wool carder bees

The Anthidium genus of Megachilidae are interesting because of the way they line their nests. Females collect, or card, plant hairs on their large, yellow mandibles to create the lining of their solitary nests in above ground or wood cavities.

Wool carder bees look a lot like what we think a bee “should” look like. The abdomen is strips black and yellow with the yellow markings not meeting in the middle. They also fly fast, making an audible buzz while foraging or hovering over flowers.

Photo of a cuckoo bee with pointy abdomen

Cuckoo bee (Coelioxys cayennensis)

Cuckoo bees

Like other families of native bees, the Megachilidae also have the outcast cuckoo bee species that do not nest on their own. Coelioxys are specialists, cleptoparasitizing nests of relatives in the Megachile species. Females use the sharp point on the end of the abdomen to pierce through nest lining to lay their eggs in the host’s brood cell. The larva will eventually develop a sickle-like jaw that it uses to kill the host egg or larva as well as any competing siblings in the brood cell.

Check out the next in the native bees series: These bees plastic-wrap their brood cells!


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