More deceptive flowers ~ Ceropegia

String-of-hearts is a well-known houseplant and the closely-related Ceropegia rendallii is found growing wild in the area where I live. I've never seen a wild one though and I bought this one from a grower. These plants also belong to the Asclepiad or Milkweed family, as do Stapeliads, and they also trick flies into pollinating their flowers. Not much was known about how Ceropegia lure the flies into their flowers, where they are trapped by downward-pointing hairs that make it impossible to escape but recent research has shed some light on a complex system involving bees and scavenger flies, such as Jackal Flies that are attracted to bees that have been attacked by predators such as Robber Flies or spiders.

These tiny flies are known as kleptoparasites and feed off of the body fluids of bees that have been caught by predators and they are attracted by distress pheromones that bees emit as they are struggling and Ceropegia flowers give off the same scents, luring the flies into the flower, where they are trapped. The fly is released from the flower when it dies and the hairs relax. The flies fly away with the flower pollen stuck to their mouthparts until they are lured into another flower, and pollination takes place.

As you can see, the flower has a funnel-shaped tube leading to a little chamber at the end, which acts as a prison for the flies that have been lured inside by what must be appetising smells (to them), only to find themselves trapped.

Further reading:
https://www.sciencedaily.com/releases/2016/10/161010052635.htm
https://www.sciencedirect.com/science/article/pii/S0367253017332735