A neat relationship exists between carpenter bees and the butterfly bush (Polygala myrtifolia): they are the exclusive pollinators of this common pioneer shrub. The flowers are a pretty mauve colour and have an unusual form – two sepals appear as wings and the central petals form a keel presenting a very distinctive end tuft. Keel-flowers have evolved structures and mechanisms to protect their pollen and this frilly crest / tuft presents as an attractant. The carpenter bee (Xylocopa caffra) lands and to access the nectar reward it’s abdomen presses the tuft downwards opening the keel to expose the stamens and anther.