Masonry Bees

Masonary bee - Osmia rufa

There are a number bee species which are commonly referred to as Masonry Bees. As their name implies these insects have a habit of building nests in old mortar, although solitary they usually appear in loose colonies - if a wall is good for one Bee, its good for others too. It is not only man made structures where Masonary bees construct their nests, they utilise almost any suitable hole . The name 'masonary bee' actually comes from the construction of the individual brood chambers out of mud.

Masonry bees are very active in May and are often mistaken for wasps due to some species appearence.

  • Risks

    The chances of being stung by a masonary bee are quite low, but they do carry stings.

    One issue with masonary bees is the damage they can cause to old mortar, by tunneling into the mortar they undermine the integrity of the mortar and ultimately the wall itself. However masoanry bees seek out the older more easily excavated mortar, mortar which should really be re-pointed anyway.

  • Treatment

    Treatment shouldn't be required for these bees, they are unlikely to sting and rarely show any aggression. They only cause minimal damage to mortar, if bees are able to dig tunnels then the mortar requires re-pointing.

    Our preferred treatment would be a direct application into each individual nesting tunnel, however residual insecticide spray treatment to the areas affected will remove a colony and hopefully break the chain, these bees often return to where they originally hatched to nest again.

  • Life Cycle

    Fertislised Queens act alone in finding a suitable nest site (holes in mortar, the ground and in wood) and then constructs a little chambers within the tunnel laying a single egg along with provisions. The queen then builds a partition out of mud and begins filling the new cell same as the last. Interestingly the eggs laid last will be males. Once she has filled her tunnel with cells she seals up the opening and may look for another site.

    When the eggs hatch they have a food source ready for them, after consuming this and pupating the young adults emerge to breed and begin the cycle again.

    There are a number of cuckoo species which lay their eggs in the nesting chambers of other bees. When the cuckoo bee egg hatches it destroys the rightful owners larvae and feeds upon the dead grubs food larder.

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