Red and blue

I always look forward to the emergence of the red mason bees (Osmia bicornis).  The first males appeared in the garden six days ago, 3rd May, precisely the same date as they appeared last year.  This, despite last year having a warm spring and this year being cold.  When the males emerge they whizz around the garden constantly checking the flowers, the bee house and all the holes in the wall for signs of a new female.  Here is one sniffing out the bee house.

In recent years there has been a two or three week delay between the emergence of the first males and the first females but this year several females were flying three days ago, 6th May.  Perhaps they were encouraged to appear early by the warm weather we have had.  I expect they mate shortly after emergence and then spend time prospecting for a nest hole.  These were checking out the bee house.

I bought some red mason bee cocoons to boost the local population and put the four smallest (assuming they would be males) and the four largest (females) in the observation wing of the bee house, hoping to watch them emerge. However, despite checking regularly I missed all the males.  I suppose it only takes a few minutes for them to chew their way out.  I must have been very lucky to see a female emerge last summer.

At the time of writing the four female cocoons have not yet produced new bees but one other female has already started building her in her chosen nest hole.  Here you can see the first cell almost complete.  This bee does seem agitated when I open the side to see what is going on so I intend to leave her in peace and only look in when I know she is not at home.  I'll post more photos when I have them.

Last winter I also drilled some holes in a couple of dead sycamores outside the front door, hoping that bees might move in.  The male red masons have been checking them out regularly.

I have also seen female red masons investigating the tree.

Then while I was watching I spotted this bee.

He looks and behaves like a red mason bee but is smaller and is the wrong colour.  He paused on the tree for a few seconds so I could take some photos.  He has a blue/green colouration with ginger fur and green eyes.  I checked in Steven Falk's field guide and then with the BWARS Facebook page and this is a blue mason bee (Osmia caerulescens), a species I have never seen before.

The female of this species is not the prettiest bee but she uses chewed up leaves (as opposed to the red mason bee's mud) to construct the cell walls in her nest.  I'll be on high alert over the next week or two trying to find a female, perhaps even in one of these holes in the trees.

All the bees, whether red or blue, have to be on guard as they look for nest holes as this one contains a nasty surprise.