Bee antics

After a slow start the bee population is building up nicely in our garden. There's always a bit of a lag phase between the first queens coming out of hibernation to forage and begin nesting and the appearance of the first workers.

Columbines Aquilegia spp. are a good source of pollen for bumblebees but they need to learn a special technique for harvesting it, by clasping the stamens with their jaws and then using their front pair of legs to rake pollen down onto their bodies. Occasionally, if it's a big bee swinging from old stamens they break free from the flower and it suddenly drops away.

This bee has full pollen baskets and is going after the nectar, which is located high up in those nectar spurs at the top of the flower, so it has to force itself right up into the flower - which must impose a lot of wear-and-tear on wings when it backs out again. 

No wonder that smarter bumblebees soon learn to bite through the nectar spurs and steal the nectar without the need for these contortions - click here to see a columbine that has been robbed in this way.

The signs are that we are in for a good broad bean crop his year, since flowering has coincided with plentiful pollinators. The flowers need to be 'tripped', forcing down the lower lip and transferring pollen to the stigma, and this common carder bee is probably not strong or heavy enough to do this efficiently. The bigger, stronger bumblebees are better, but they soon lean to steal nectar by biting through the corolla tube, as you can see by clicking here.

Many years ago I carried out a lot of research in broad ban breeding and grew large trial plots. The scent of their flowers early in the morning is exquisite and very strong; there is an ancient legend that you would hallucinate if you fell asleep in flowering broad bean crop; click here for more on the folklore of this plant. 

The biggest 'bee magnet' early in the year has been alkanet Pentaglottis sempervirens, which I couldn't stop growing even if I wanted too, as it's somewhat invasive and, like dandelions, re-sprouts from small pieces of root left in the soil. It has recently been visited by this bee, which I think is the red mason bee Osmia rufa - a rare visitor to our garden, although I have seen its nest tunnels in mortar in the walls of a house not far away.

You can see the distinctive 'horns' on the face here and the large jaws  - used for collecting mud to plug their nest chambers.

I think I'll install some nest tubes like these to see if it can be coaxed to breed in the garden.

Nectar Nicked

A couple of days ago I posted some pictures of bumblebees stealing nectar from columbine flowers without pollinating them. They're at it again, this time on my broad beans.

This is a well-behaved bumblebee, showing how it should be done. The bee lands on the flower and pushes its head into the gap between the standard petal and the wing and keel petals below, reaching out with its tongue towards the nectar in the corolla tube behind the petals.

This requires a lot of physical effort on the part of the bee, and in forcing its tongue towards the hidden nectar it also forces down the two wing petals (with the black blotches on them) and springs the stigma and stamens from the keel petal that encloses them. The half-full pollen baskets show that this industrious bee is also collecting pollen for the brood, as well as satisfying its own energy requirements with a drink of nectar; textbook behaviour.

After the bee leaves the flower should look like this, with the stamens and stigma tripped and protruding from the enclosing keel petal, with pollen forced onto the surface of the stigma so that there's every chance that a broad bean pod will now develop.

And here's the sneaky way to extract nectar without all the effort required to trip the flower - simply by biting through the corolla tube and poking your proboscis through the hole. This bee seems to have no pollen baskets so I think it may be a cuckoo bee, stealing nectar wherever it can find it, leaving the flower untripped. I don't suppose I'll be picking many beans from this plant.