Why do some fly-pollinated orchids smell like decaying matter?

Some fly-pollinated orchids emit odors resembling decaying matter as a form of deception to attract specific pollinators. By mimicking the scent of carrion, dung, or other putrescent substances, these orchids lure scavenging flies that are naturally drawn to such materials to feed or lay eggs.12

This strategy is a highly specialized evolutionary adaptation. While some orchids attract flies with sweet scents and nectar, others rely entirely on this "rotten" mimicry to ensure pollination without providing any food reward to the insect. To enhance this deception, these flowers often feature:1

• Visual Mimicry: Many species have dull, mottled, or checkered colors in shades of green, brown, purple, or red, which resemble decaying flesh or fungi.12
• Structural Guides: Flowers may possess specialized shapes, such as large landing surfaces, "tails," or motile hairs that vibrate in the wind to further attract and guide the flies.1
• Trapping Mechanisms: Some orchids utilize hinged lips or saccate (pouch-like) structures to temporarily trap the flies, forcing them to crawl past the flower's reproductive organs to escape, thereby ensuring the transfer of pollen.1

This process effectively exploits the flies' natural foraging or reproductive behaviors to facilitate the orchid's reproduction.12