May 062020

The mason bees (Osmia bicornis) in our garden are still active with the female bees provisioning their mud cells with pollen. In my last post I said that there did not seem to be much sexual selection going on – as I released a female she was immediately grabbed by a male. But I have been watching the males more closely. I think that they might be engaging in aerial combat with other males. Chasing them off so that they retain their own piece of space – first female in their airspace is theirs to mate with. Of course, I might be writing rubbish! But I have seen other males persistently dive bombing a copulating couple and, it seems to me, that they are trying to give the male a slap on the backside. I doubt this is meant to be helpful. Once the males are out of the way the female brings in pollen, not on her legs as other bees do, but under her abdomen. In our garden they are collecting bright yellow pollen which makes the returning females rather beautiful.

We tried to follow the bees to identify the pollen source but Sally lost sight of them as she (Sally) tried to get over our neighbour’s 6ft fence. Sadly, she is not as nimble as she once was! Once there is enough pollen in a cell the female comes out of the tube, turns round, and reverses down the tube to lay an egg. The females are incredibly industrious – this female spent 2-3 days to complete the long row of cells shown here (the entrance is to the left). If you look carefully you will see that all cells with the egg and pollen are not the same and the last one on the left is quite different. Lots of biological questions!

The flies (Cacoxenus indagator) have been very numerous around the nesting tubes. They must cause a lot of bee mortality. But the cast of players in this story is getting bigger and the flies do not have everything their own way. This small spider (no idea what it is) has made a rough web next to the tubes and here it has just caught one of the flies. I think the spider might be too small to go for the bees themselves.



Another spider that we often see on this wall is the small Zebra spider. These are hunters with forward looking eyes. They prowl about and jump on their prey. Again I don’t think the spider would go for a bee – a fly would do nicely.


Finding this solitary wasp was a real surprise. It has the splendid name of Sapya quinquepunctata (Fabricius), 1781. This one is a male – the females should be around soon. They are kleptoparasites which means the female will lay her egg in the cell of the mason bee and her larva will kill the bee egg and then eat the pollen. Neat trick! Needless to say I had never heard of this species. But I have given its full name because I think it is amazing that 240 years ago, a Danish entomologist named Johan Christian Fabricus found this insect and described and named it! He did the same for almost 10,000 different species!


However, I have saved the best new player on the stage until last. I don’t what it is called.  And although I know that it is a Pteromalid parasitic wasp I don’t know what it goes for. It is very small about 2-2mm and I have already spent one afternoon looking at it through a microscope – but I am none the wiser (yet).

All of this is going on in our garden. Which makes me glad they we have lots of wildflowers producing pollen. I am glad that we don’t use herbicides and nasty pesticides that kill stuff and damage the brains of bees. The biodiversity is beautiful. Thanks to Sally for the photographs.


 Posted by on 6 May 2020 at 2:21 pm

  One Response to “More about Mason Bees”

Comments (1)
  1. Great article Malcolm.
    Trying to get the image of Sally trying to get over a 6ft fence out of my head.

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