As for your wondering if they’d nest in September – I gather it was a bit tongue in cheek (an you know your bees better than I)… however to be clear to any others who may read this, as the variety of bees species (especially the reported 20,000 solitary bees) and insects is down to their co-evolution with specific plants and flowers and nesting habitats, to see a particular species at a certain time certain conditions need to come together – accessible food, consistent temperatures, nesting materials and safe habitats.

For example, my main population of Mason bees (Osmia cornuta) have evolved to emerge with fruit tree blossoms – plums and cherry trees especially. The population found their safe habitat in the brick walls because of the type sandy mortar used in the farmhouse buildings of the village, along with the planting of fruit trees by the farmers. Correspondingly they only emerge once a year with the spring blossoms – the adults fly and nest over a variable six-week period in March to May when above 15°C, they locate wet mud sources, and lay eggs on pollen and nectar stocks (that they have deposited in tunnels) and then seal the cells. The eggs hatch within a matter of days. These larvae feed on the ‘bee bread’ left by the nesting females, and within four weeks (early as June) when their food stock is eaten, will spin white silk cocoons . These moist cocoons eventually darken and dry to a light brown colour (probably from the surrounding excrement in the cell). They metamorphose from larvae to young bee inside the cocoon and emerge as adults in the spring of the following year. In Northern hemisphere climates, most solitary bees only have a yearly cycle, although I have read somewhere that some species may have two.

As we have seen from when I filmed the Wool Carder Bee (5 weeks ago), their flying period is in July because of the flowers (lavender, Globe Thistle Echinops Ritro etc.) that they prefer/have co-evolved with. I am not sure that because of the ‘wool’ that the females gather that they could be classified as mason bees even if they do use or excavate tunnels. Another example of adaptability to the environment would be leaf-cutter bees which exist later in the spring and into the summer, and corresponding use leaves of roses and other plants to create their cells and seal their tunnels.

So to have a population of solitary bees in September, there needs to be a combination of the right flowers (year in year out) that match their feeding apparatus, consistent temperatures (I note that bees tend to get smaller as the temperature rises, what scientists call surface-area-to-volume-ratio issues), and the right nesting habitats.

So.. as to whether there is sufficient and consistent availability of wet mud for the mason bees late in the summer is questionable. However I do hope you do see other bees around.

In respect of the purchased plastic-based habitats, there was a strong smell of plastic the ‘off-gassing’ from the materials used. This unnatural aroma led me to think that it might put off the bees who normally seek holes in wall or tress, so yes having left the untouched habitats outside over winter (2009/10) has meant that the gases are less strong.

One mason bee did take up the opportunity last year but it’s progeny didn’t return to nest in the habitat. However this is probably due to the fact that (despite it being exposed to the afternoon sun) it was North facing and the bee prefer morning sun. I left it there, because I have begun to realise that to expand my bee population I must be able to to clean out the parasites in the tunnels. If not, the young bees can get blocked by failed cells, get pollen mite infestations, or the Cacoxenus indagator (bee flies – see my post) would start to really infest the habitats (as they did in 2008) and thus put a brake on the bee population expansion. So you do need to be able to disinfect the tunnels without harming the bee cocoons inside (hence my choice of habitats since).

For your other questions: The white plastic insert habitats were designed to be flush with the wood, so they are essentially ‘sealed’. Other habitats were much more successful however, but I put this down to the choice of habitats that they have – wood drill blocks, brown paper tubes and reed/hollow-stem plants (pond reeds, dried hogweed and Japanese Knotweed +). It means that mean the bees (and different species that arrive at different times) can choose to nest and remain where they are most comfortable. My own bee observation boxes (using 10cm cut of narrow plastic hose) have no off-gas problems and are sealed at the back by the wooden dowelling that hold them in place in the hinged roof box.

Thanks for commenting.