Mason bee

Mason bee
Osmia rufa
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Megachilidae
Subfamily:	Megachilinae
Tribe:	Osmiini
Genus:	Osmia Panzer, 1806
Species
Osmia atriventris Osmia bicolor Osmia californica Osmia cornuta Osmia lignaria Osmia ribifloris Osmia rufa

Mason bee is a common name for species of bees in the genus Osmia, of the family Megachilidae. They are named from their habit of making compartments of mud in their nests, which are made in hollow reeds or holes in wood made by wood boring insects.

Species of the genus include the orchard mason bee, Osmia lignaria, the blueberry bee, O. ribifloris, and the hornfaced bee, O. cornifrons. The former two are native to the Americas and the latter to Japan, although O. lignaria and O. cornifrons have been moved from their native ranges for commercial purposes. The Red mason bee, Osmia rufa, is found across the European continent. There are over 130 species of mason bees in North America that are active from spring through late summer.

Spring mason bees (blue orchard and hornfaced) are increasingly cultivated to improve pollination for early spring fruit flowers. They are used sometimes as an alternative, but more often as an augmentation for European honey bees.

Unlike honey bees (Apis), they are solitary; every female is fertile and makes her own nest, and there are no worker bees for these species. Solitary bees produce neither honey nor beeswax. They are immune from acarine and Varroa mites, but have their own unique parasites, pests and diseases.

Most mason bees live in holes and can be attracted by drilling short holes in a block of wood. Blue orchard and hornfaced bees are excellent spring season pollinators and, since they have no honey to defend, will only sting if squeezed or stepped on. As such, they make excellent garden "pets", since they both pollinate the plants and are safe for children and pets.

A word of caution. To successfully raise mason bees, it is important to know the condition of the over-wintering cocoons. With drilled blocks of wood, you can not assess their health. As a result, pests can overtake the holes resulting in no or less surviving mason bees. It is advised to either place a paper insert into each drilled hole, or use straws/reeds/wood trays, any of which can be obtained through nurseries or online websites.

Harvesting cocoons in the fall helps reduce pests. Opening a portion of your straws will show pests (pollen mites, chalkbrood, etc.) that are present. There are websites that show you specifically what to do and what to look for. It is actually quite easy.

Osmia species are usually metallic green or blue, though many are blackish. Most have black ventral scopae which are difficult to notice unless laden with pollen. They have arolia between their claws unlike Megachile or Anthidium species. The number of Osmia species in North America is probably third in line after Andrena and Perdita.

Life cycle

Home made nest block showing full occupation

Mason bee nest cell with egg on pollen bed.

Mason bee nest cell with cocoon.

Hornfaced bee Osmia cornifrons

The bees emerge from their cocoons in the spring, with males the first to come out. They remain near the nests waiting for the females. When the females emerge, the first thing they do is mate. The males die and the females begin provisioning their nests.

Osmia females like to nest in narrow holes or tubes, typically naturally occurring tubular cavities. Most commonly this means hollow twigs, but sometimes other similar spaces are used, including empty snail shells (they do not excavate their own burrows, unlike many bees). The palearctic species O. avosetta is unique for building burrow nests of flower petals. A female might inspect several potential nests before settling in.

Females then visit flowers to gather pollen and nectar, and it will take many trips to complete a pollen/nectar provision mass. Once a provision mass is complete, the bee backs into the hole and lays an egg on top of the mass. Then she creates a partition of "mud", which doubles as the back of the next cell. The process continues until she has filled the cavity. Female-destined eggs are laid in the back of the nest, and male eggs towards the front.

Once a bee has finished with a nest, she plugs the entrance to the tube, and then may seek out another nest location.

By the summer, the larva has consumed all of its provisions and begins spinning a cocoon around itself and enters the pupal stage, and the adult matures either in the fall or winter, hibernating inside its insulatory cocoon. Most Osmia species are found in places where the temperature drops below 0°C for long durations, like Canada, and they are well-adapted to cold winters.

See also

• Orchard mason bee
• Osmia californica
• http://en.wikibooks.org/wiki/Beekeeping/Solitary_Bees

External links

• Instructions for Mason Bee Housing
• Osmia Identification Guide (female)
• Osmia Identification Guide (male)
• List of Species
• Worldwide Species Map
• Red Mason Bee
• Products & Success with raising mason bees
• Palaearctic Osmiine Bees

Further reading

Pollination with Mason Bees, Dr. Margeriet Dogterom