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.