Why is the pretty, red bug standing on this thistle flower?
This is an immature Milkweed Assassin Bug. They wait on flowers until a bee, fly, or butterfly comes for some nectar. Then the Assassin Bug pounces on them. It stabs them with its sharp, beak-like mouth, and squirts saliva into them. This saliva is lethal to insects, killing them, and liquifying their insides. This liquid is then sucked up by the Assassin Bug.
In spite of the fact that they can deliver a very painful bite to humans if handled, they eat so many pests that most gardeners are glad to have them around.