The chocolate industry is built on the labour of bloodsucking midges

Jun 17th 2026|3 min read

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The world’s chocolate industry boasts revenues of more than $140bn. In recent years the market for cacao beans, the crucial ingredient, has often been tight. In April 2024, after poor harvests in West Africa, the price passed $10,000 per tonne for the first time. Although it has fallen back since, it remains significantly higher than earlier in the decade.

A good time, then, for the world’s farmers to try to boost their harvests. One way would be to pollinate their existing plants more efficiently, so as to produce more of them in the next generation. There is a problem, though: no one has been quite sure how cocoa plants are pollinated. Now, though, work by Eliza Van de Sande, a PhD student at Vrije University in Brussels, and published in Basic and Applied Ecology, suggests that a group of tiny blood-sucking midges are essential to the process.

Many plants rely for pollination on an evolutionary bargain with animals. The plant produces high-energy nectar that entices animals (usually insects) to visit. But to get it, an animal must venture inside a flower. As it does it gets covered in pollen, while also shedding pollen stuck to it by other plants. Farmers often try to enhance the process by making their farms attractive to pollinating insects.

The reason cacao pollinators have remained mysterious is mostly because of anatomy. Cacao flowers are very small, structurally complicated and hidden by hoods that make it tricky to see what is going on inside. To make matters worse, many of the visitors to cacao plants are minute fly species that are notoriously hard to identify.

Ms Van de Sande and her colleagues observed insects visiting cacao flowers on farms in Malaysia and French Guiana. Rather than simply counting the visitors, as most previous studies had done, the team opened and inspected the flowers. Any insects inside were observed to work out whether they were interacting with the reproductive parts of the flower. The insects were then captured and checked to see if they were carrying cacao pollen.

Ants, bees and midges all turned up inside the flowers. But of the 449 insects that the researchers collected, 439 were midges. Of those, 185 were biting midges that were often seen interacting with plant reproductive organs and were covered in cacao pollen about a third of the time. Few of the other bugs showed much evidence of doing anything for pollination.

Those results strongly suggest that biting midges are the dominant force behind cacao pollination. They might therefore be a useful focus of efforts to enhance production. Ms Van de Sande and her colleagues also found that the midges were far more active when it was cool and humid. That could be bad news for cacao farmers, because—thanks to climate change—many of their plantations have been getting warmer and drier.

Luckily, they have options. Ms Van de Sande points out that “agroforestry” techniques, in which native trees are grown on plantations to provide shade, lower temperatures and increase humidity could be one way to encourage more pollinators to move in. Admittedly, trying to encourage more bloodsucking midges might be a hard sell for farmers themselves. But it might improve their yields. ■