Flies are often dismissed as mere pests, yet they are indispensable actors in the complex web of ecosystems. While the hum of a bee is the archetypal sound of pollination, the persistent drone of a fly against a windowpane represents a different, equally vital ecological service. These insects, belonging to diverse families across the order Diptera, are significant contributors to the pollination of numerous wild plants and commercial crops. Understanding what do flies pollinate reveals a world where fuzzy bodies and opportunistic feeding habits translate into the fertilization of plants that form the basis of our food supply and natural landscapes.
The Mechanism of Fly Pollination
Unlike honeybees, which actively collect pollen to feed their young, most flies are pollen incidentalists. They visit flowers primarily for nectar, a high-energy sugar source, or for shelter. As a fly crawls into a flower in search of this reward, its body, particularly the fuzzy hairs of its abdomen or legs, becomes inadvertently coated with pollen grains. When the fly moves to the next flower of the same species, some of this pollen rubs off, facilitating cross-pollination. This process, known as pollination by non-flying insects or "myrmecophily" in a broader sense, is highly effective for plants that do not require the precision of a bee.
Physical Adaptations for Pollination
Several fly families have evolved specific physical traits that make them efficient pollinators. Syrphid flies, or hoverflies, are perhaps the most recognizable. They are often brightly colored with yellow and black stripes, mimicking wasps to deter predators, and are covered in dense hairs that trap pollen effectively. Their constant hovering behavior allows them to access flowers quickly and move between them with agility. Other families, like bee flies (Bombyliidae), are robust and fuzzy, directly resembling bees, while fungus gnomes are small and adept at navigating the tight spaces of low-growing flowers.
Categories of Plants Pollinated by Flies
The plant world is replete with species that have forged mutualistic relationships with flies. These plants often share common characteristics that appeal to the insects' preferences. They typically feature open, accessible flowers with little to no landing platform, shallow blossoms, or flowers that trap the insect temporarily. Many emit a distinct odor that mimics decaying matter, fungi, or carrion—the very scents that attract flies to their natural food sources.
Early Bloomers: Many flies are active even in cool spring temperatures when bees are less active. Plants like Skunk Cabbage (Symplocarpus foetidus) and Buttercups (Ranunculus spp.) rely on these early-emerging insects to get their reproductive cycle started.
Carrion and Dung Mimics: Flowers such as Corpse Flower (Amorphophallus titanum), Starfish Flower (Stapelia gigantea), and Pawpaw (Asimina triloba) emit powerful odors of rotting flesh or dung. They not only attract flies for pollination but also sometimes trap them temporarily to ensure pollen transfer.
Wind-Pollinated Alternatives: In environments where wind pollination is common, some plants utilize flies as a backup or supplementary method, ensuring genetic diversity.
Economic and Ecological Significance
The impact of flies extends far beyond wild flora. Numerous commercial crops depend on the unsung work of these insects. Blueberries, cranberries, cherries, and plums are all known to benefit significantly from fly pollination, often seeing increased fruit set and quality when flies are present in orchards. Furthermore, flies are the primary pollinators for a variety of wild plants that form the foundation of food webs. They contribute to the biodiversity of meadows, forests, and wetlands, supporting the growth of seeds and fruits that feed birds, mammals, and other organisms.
