Revisiting cacao pollination: new behavioural and pollen-based evidence for the key role of Ceratopogonidae

Poor pollination success is an important limiting factor for cocoa production globally. Historically, cacao pollination has been attributed to biting midges (Diptera: Ceratopogonidae). However, recent studies have reported a broader diversity of insects visiting cacao flowers, leading to renewed debate over the identity and ecological relevance of its pollinators. Here, we provide new behavioural and pollen-based evidence supporting biting midges as the likely dominant pollinators of cacao. We combined detailed observations of insect activity on cacao flowers with assessments of pollen presence on insect bodies and developed a trait-based decision tree to distinguish likely pollinators from incidental flower visitors. Biting midges were substantially more active on cacao flowers than other dipteran visitors, frequently contacted reproductive structures, and exhibited markedly higher rates of pollen attachment. These findings are consistent with earlier work from the 1970s and 1980s suggesting that cacao may rely on a narrower taxonomic group of pollinators than is currently assumed. Although pollination success was not directly quantified, our results provide mechanistic evidence that narrows the pool of likely pollinators and helps reduce bias associated with visitation-based approaches. More broadly, this study demonstrates how trait-based approaches can improve the distinction between functional pollinators and incidental visitors in plant species where direct measurement of pollination is challenging. Future research should refine which Ceratopogonidae genera and species are responsible across production regions and characterise their ecological requirements. Such knowledge will be essential for managing pollination as a key ecosystem service in tropical agroecosystems and for designing resilient production systems under changing climatic conditions.