Osmia rufa – the good, the bad and the uncertain

Male Osmia rufa in Lilac 28.4.13

Male Osmia rufa in Lilac 28.4.13

Before I go any further I think I should call my seventh identification Osmia bicornis as that is what BWARS uses.  I was particularly happy to see it in the garden this year as I had never seen it before.  The only mason bee to have occupied my old nest box was Osmia cornuta but more about her later.

Male Osmia bicornis diving into Lilac flowers

Male Osmia bicornis diving into Lilac flowers

The above image does not serve any identification purpose but I inserted it as I think it is cute as he stretches to reach the nectar deep in the flower.  It does, however, show he is infected by mites which will probably not cause him any harm and he should have served his purpose by fertilising the females now hard at work building their nests.

Osmia bicornis female 17.4.13

Osmia bicornis female 17.4.13

The Osmia bicornis females have two prongs on their face under their antenna.  The left one can be seen in profile in the image above but the black prongs do not come out well against the black head of the bee.  These are used to tamp in the mud they use to cement up the cells containing their eggs supplied with pollen and nectar.

In due course the eggs will hatch and the larvae will consume their provisions and go on to spin a cocoon in which they will pupate.  About 14-15 weeks after the egg has been laid, the adult bee will be formed.  The bee passes the winter in the adult form to emerge in the spring.

Now comes the good part.  I can become despondent at my lack of knowledge as I trawl through the internet or painstakingly try to make sense of an identification key.  Then the other day I found some pictures I had taken in a wood three kilometres from here about two years ago.

Osmia bicornis mating in Asphodel 13.4.2011

Osmia bicornis mating in Asphodel 13.4.2011

I was delighted to capture an image of the fluffy bees and at the time I thought they were bumble bees!  I soon realised they were not bumble bees but some sort of solitary bee.  As soon as I re-opened the file the other day I recognised them as Osmia bicornis.  That cheered me up!  It is a slow process but I am improving.

You can hardly see the female from the angle I have taken the photograph although she is considerably larger than the male.

Osmia bicornis.18.4.13

Osmia bicornis female.18.4.13

A new fixed bee hotel had been placed on the garden wall and attracted many more insects than the little, old one which hangs under the Lilac tree.  So the sunnier spot was probably the reason I was able to attract the O. bicornis for the first time.  In addition, every year I add more plants to provide pollen and nectar for the bees.

However, they fly very quickly and I was not pleased with the photographs and I am uncertain as to how to improve them.  The above photograph was taken at 1/1000 s. ISO 4000 and f 6.3.

Osmia bicornis and flies.16.4.13

Osmia bicornis and flies.16.4.13

Here I had tried ISO 320 and 1/500s. but with f 3.5, the depth of field is too short.

Hemaris fuciformis 7 May 13

Hemaris fuciformis 7 May 13

Here I have just succeeded in showing the wings of the Hummingbird Hawk Moth (wing beat frequency between 25-45 beats a second) that visits the garden by using 1/1250 s. ISO 2000, f9.  There always seems to be a play-of between quality, speed and depth of focus when the light is not strong.  I think a minimum of f9 is required but there is not always enough light to reduce the aperture sufficiently.

The highest speed my camera synchronises with flash is 1/125 s. I would love to hear if anyone has any ideas on how to improve on bee shots.

The bad news is that there were quite a lot of little flies hanging around while the O. bicornis were building their nests.  They just looked like fruit flies to me but I was suspicious never the less.  I now realise that it is very likely that these flies were Cacoxenus sp. which are parasites of Osmia.  I shall have to make a pooter (aspirator) before the next mason bee season and consider renewing the bamboos annually although this will not deal with the problem of the flies.

Advertisements

2 thoughts on “Osmia rufa – the good, the bad and the uncertain

  1. Don’t worry too much about the flies. Most dipteran parasites of bee nests are cleptoparasites ie their larvae live of waste material in the nest, so don’t interfere with the bees’ lifecycle at all (if anything, benefit it by tidying up). I can’t remember if Cacoxenus fall into this category, but if they are not endoparasites, they are not a problem.

    Like

    • Unfortunately, from what I could see they looked like Cacoxenus indagator which I have read is responsible for 50% of parasitism of Osmia. You are correct it consumes the pollen and nectar put down for the bee larvae but stops the development of the egg.

      Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s