A hoverfly found something to eat in this fragile blue flower.
It's a Blue Lettuce (Lactuca perennis). It likes warm and sunny places, so you only find it on well-exposed hillsides and fields. The flowers open only when it is sunny.
The rosettes look like those of the common Dandelion, but the leaves are a bit more incised. Like those, and also like the garden lettuce it has a white latex.
The shadow of another insect.