Mason Bee Nests - Multi-occupancy

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Ed Phillips
Last seen: 4 years 12 months ago
Joined: 13/05/2012 - 08:41
Mason Bee Nests - Multi-occupancy

I was monitoring my garden "bee-hotel"; paying particular interest to the few Osmia leaiana nests that were completed during 2013. A hole was being gnawed in the chewed-leaf plug sealing one of the nests, so I stayed around to observe. During a one hour period, a male Osmia leaiana appeared, then a female, then a parasitic Sapyga quinquepunctata wasp. The wasp had to retreat into the hole as a female Osmia bicornis entered and started removing nest debris (see composite photo). The next time I looked, I could see that the bicornis female was nest building. I speculated that there may well be further leaiana brood cells remaining deeper in the hole and wondered what would happen to them.

Today, I noticed a hole appearing in another one of the recently-completed bicornis nest holes. I was intrigued, because all the bicornis from last year had emerged weeks ago. I waited and was interested to see what looked like a male Osmia leaiana emerging (second photo). This was definitely a bicornis nest because it was sealed with mud. It would appear that Osmia species multi-occupancy can occur in these holes. I think that after some outer-most leaiana (and cleptoparasites!) have emerged, holes are "high-jacked" by bicornis females who utilise the vacated portion of the hole. The male leaiana that I saw emerging from the second hole, would (presumably), have had to break through several bicornis brood cells to get to the surface. Has anyone else witnessed this?

Last seen: 3 years 4 months ago
Joined: 23/05/2013 - 13:02
Red mason and leaiana

Hi Ed,

I have found that later in the red mason season, red mason females with seal the out parts of cavities with mud even if the whole of the cavity is unused completely. They could also seal the out ends of cavities that have other species inside them. Cheers, George

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