Which flowers need flies for pollination?

The flowers of the stapelia in the genus Stapelia of the family Apocynaceae are the largest flowers among succulents, with a maximum diameter of up to 36 cm. The biggest difference between stapelia flowers and the flowers of other plants is that they need flies for pollination, rather than the bees and butterflies we are familiar with. This is because stapelia flowers have a special odor, so what they attract is flies.

Stapelia is native to the arid tropical regions of South Africa and is a perennial succulent herb. The stems are thick, four-angled and ribbed, with tooth-like protrusions and very short soft hairs along the ribs, grayish green, growing upright. The stapelia flower is five-angled, like a starfish, purplish red, with more than 10 large flowers, and the flowering period lasts about a week.