Which major orchid groups are mainly pollinated by flies?

Three major groups of orchids have become predominantly pollinated by flies:

• Pleurothallidinae: A subtribe found in tropical America that contains more than 4,000 species.1
• Bulbophyllum: A group comprising about 1,800 species, primarily located in the Old World.1
• Pterostylis: A large genus and its relatives found in Australia.1

These orchids often employ specialized adaptations to attract flies, such as mimicking decaying substances, dung, or carrion to deceive the insects. Their flowers frequently feature dull colors, putrescent odors, and complex mechanical structures—such as traps, hinged lips, or motile hairs—designed to guide flies toward the reproductive organs.1