Which plant species requires the giant hawkmoth (Xanthopan morganii) for pollination due to its 30 cm floral spur?

• A. Queen of the Night cactus.
• B. Elbow Orchid.
• C. Moonflower.
• D. Madagascar star orchid.

Answer: (D)

A very long nectar spur is a classic example of specialized plant–pollinator coevolution: the flower evolves a spur that only a pollinator with a matching long proboscis can reach, ensuring efficient pollen transfer. The Madagascar star orchid has a spur about 30 cm long, a length that only a giant hawkmoth like Xanthopan morganii can access. As the moth probes the nectar, its long mouthpart reaches the nectar and brushes against the flower’s reproductive surfaces, grabbing pollinia and, on visiting another flower, depositing them to effect cross-pollination. This tight physical match makes the orchid highly dependent on that specific moth. The other plants listed can be pollinated by nocturnal moths as well, but they don’t require such an extreme spur length, so they don’t depend on the giant hawkmoth in the same way.