Yes, many flies eat plants, though the way they do it depends heavily on their life stage. Adult flies typically feed on nectar and pollen from flowers, while fly larvae are more likely to chew through leaves, burrow into fruit, or tunnel through roots. With over 150,000 known species of flies worldwide, their plant-feeding habits range from gentle pollination to serious crop destruction.
How Adult Flies Feed on Plants
Most adult flies that visit plants are after nectar, the sugar-rich liquid flowers produce. Hoverflies (also called syrphid flies) are the most familiar example. These black-and-yellow-striped insects hover like tiny hummingbirds over flowers, using a flexible tube-like mouthpart to drink nectar from blossoms. There are over 6,000 species of hoverflies worldwide, and nearly all adults feed on nectar regardless of what their larvae eat.
Female hoverflies also eat pollen, which provides the protein needed for their eggs to develop. The length of a fly’s mouthpart determines which flowers it can access: species with longer mouthparts reach nectar deep inside tubular flowers, while short-mouthed species stick to open, shallow blooms like daisies and Queen Anne’s lace. Bee flies, dance flies, and many other fly families follow similar patterns, visiting flowers regularly for nectar and pollen.
Some adult flies feed on plant sap that oozes from wounds in tree bark or damaged fruit. Others land on overripe or fermenting fruit to lap up the sugary juices. The common housefly doesn’t eat living plant tissue, but it will readily feed on decaying plant matter using its sponge-like mouthparts to dissolve and absorb nutrients from the surface.
Fly Larvae That Feed on Living Plants
The real plant-eating happens at the larval stage. Fly larvae (maggots) from several families are dedicated herbivores that feed on living plant tissue from the inside out.
Leafminer flies are among the most widespread plant feeders. The adult female lays eggs on or inside a leaf, and the newly hatched larva burrows between the upper and lower surfaces, eating the soft tissue in between. As the larva grows, it leaves a visible trail: a winding, S-shaped tunnel called a serpentine mine, or a wider blotchy patch where tissue has been consumed. These mines get larger as the larva matures, eventually forming blisters or pale, papery patches on the leaf. Several leafminer species attack vegetable crops, including spinach, peas, and a range of ornamental plants. The spinach leafminer, for instance, feeds inside the edible portion of the leaf, making the crop unmarketable.
Gall midges take a different approach. These tiny flies lay eggs on stems, leaves, or buds, and the developing larvae release chemicals that cause the plant to grow abnormal tissue around them, forming a hard, rounded structure called a gall. The larva lives inside this gall, feeding on the nutritious tissue the plant was tricked into producing. Hundreds of gall midge species target specific plants, from roses to wheat.
Root maggots feed underground, chewing through the roots of crops like cabbage, onions, and carrots. The damage often goes unnoticed until the plant wilts or dies from losing its root system.
Fruit Flies and Crop Damage
Fruit flies cause some of the most economically significant plant damage of any insect group. The Mediterranean fruit fly is considered one of the most destructive agricultural pests in the world. It can infest apples, avocados, bell peppers, melons, tomatoes, and many other crops. The female punctures the skin of the fruit to lay her eggs inside, and the larvae feed on the pulp as they develop. Infested fruit decays early, drops from the tree, and is completely inedible.
The economic stakes are enormous. Countries spend millions on surveillance, quarantine programs, and eradication efforts to keep fruit flies out of agricultural regions. A single outbreak in a major growing area can shut down exports and destroy an entire season’s harvest. Other fruit fly species target cherries, blueberries, olives, and citrus, each specializing in particular crops.
Flies as Pollinators
While some flies damage plants, others play a crucial role in helping them reproduce. Hoverflies are the world’s second most important group of pollinators after bees. As they move from flower to flower drinking nectar and eating pollen, they transfer pollen grains between blossoms, fertilizing the plants in the process. The economic value of all insect-mediated pollination globally was estimated at roughly $780 billion in 2016, and hoverflies contribute a substantial share of that figure.
Flies are especially important pollinators in cold or wet climates where bees are less active. In alpine meadows, arctic tundra, and cloudy coastal environments, flies often do the majority of pollination work. They also pollinate many crops grown in greenhouses, where their tolerance of enclosed conditions makes them effective alternatives to bees. Some plants have evolved specifically to attract flies rather than bees, producing flowers with dull colors or strong odors that mimic decaying material.
When Plants Eat Flies Instead
The relationship sometimes runs in reverse. Carnivorous plants like Venus flytraps, sundews, and pitcher plants capture and digest flies to supplement their nutrition. These plants typically grow in nutrient-poor habitats like bogs and wetlands, where the soil lacks the nitrogen and phosphorus they need. Their modified leaves function as traps, using sticky surfaces, snap mechanisms, or slippery pitfall chambers to catch insects.
Once a fly is trapped, specialized glands on the plant’s surface secrete digestive enzymes and acids that break down the insect’s body. The same glands then absorb the released nutrients directly through the leaf surface, functioning much like a simple digestive system. A single Venus flytrap leaf can take about 10 days to fully digest a fly before reopening for the next meal. For these plants, flies aren’t a food source so much as a fertilizer delivery system, compensating for what the soil can’t provide.