While bees, butterflies, and hummingbirds are widely recognized for their contributions to plant reproduction, pollination involves a diverse array of organisms. This biological interaction is essential for the continuation of many plant species, ensuring pollen transfer for fertilization and seed production. Often overlooked in this process are flies.
Flies as Pollinators
Flies, belonging to the order Diptera, play a substantial role in plant pollination. This diverse group includes:
- Hoverflies (Syrphidae)
- Bee-flies (Bombyliidae)
- Midges (Chironomidae)
- Some mosquitoes
These insects are often present in ecosystems where other pollinators are scarce. Flies are considered the second most significant group of pollinators globally, after bees.
How Flies Pollinate
Fly pollination, also known as myophily, occurs incidentally when flies visit flowers. As adult flies forage for nectar or pollen, their bodies inadvertently pick up and transfer pollen grains. Many pollinating flies, such as hoverflies and bee-flies, possess hairy bodies that effectively collect pollen. Unlike bees, which actively gather pollen for their offspring, flies are often unintentional in their pollen transfer. While less efficient per visit than specialized pollinators, their sheer numbers and frequent flower visits can compensate for this difference.
Flies exhibit various feeding behaviors that facilitate pollen transfer, including lapping nectar from open flowers or consuming pollen directly. Some flies, like bee-flies, have elongated mouthparts that allow them to access nectar from tubular flowers. This incidental transfer of pollen contributes to the reproductive success of numerous plant species.
Plants That Attract Flies for Pollination
Many plants have developed specialized adaptations to attract flies for pollination. These “fly flowers” often display characteristics that appeal to the flies’ foraging habits, such as seeking decaying organic matter or fungi. Common traits of fly-pollinated flowers are dull colors like maroon, brown, or green, sometimes with translucent flecks. They frequently emit strong, foul odors mimicking carrion, dung, or fermentation, which draws flies looking for food or egg-laying sites.
Examples of plants that rely on flies include Arum lilies, skunk cabbage, and some orchids like the Dracula orchids. Dracula orchids, for instance, mimic the appearance and scent of mushrooms to attract mushroom-specialist flies for pollination. Economically important crops such as cacao are also primarily pollinated by tiny flies known as midges. These midges are uniquely suited to navigate the small, intricate flowers of the cacao tree, which grow directly from the trunk and branches.
The Ecological Importance of Fly Pollination
Fly pollination holds ecological importance, particularly in environments where other insect pollinators are scarce. In regions such as the Arctic and alpine zones, flies are often the dominant group of pollinators. Their presence contributes to the biodiversity and stability of these ecosystems.
Flies also play a role in food security. They are pollinators for over 100 types of crops, including onions, carrots, and avocados. The reliance of cacao trees on midges for pollination means flies are essential for chocolate production. For some plant species, flies are the sole or primary pollinators.