How do flowers provide food for many adult flies?

Flowers provide essential nutrition for many adult flies by offering water, nectar, and pollen.1

• Nectar: Most adult flies consume this syrupy liquid, which serves as a vital source of carbohydrates.1
• Pollen: This is a rich source of protein, which is particularly important for adult flies to compensate for nutritional shortcomings from their larval stage. Because pollen can be difficult to obtain, some flies, such as certain hover flies, crush the grains with their labella before swallowing them, while others probe flowers and collect pollen on their heads and eyes.1
• Specialized Secretions: Some plants, such as the cuckoopint, attract flies with fetid odors and trap them within a floral chamber. Inside, the flies feed on nutritious stigmatic secretions produced by the plant.2

Flowers have evolved specific attractants, including scents, colors, and nectaries, to entice these insects, while flies have developed specialized mouthparts to extract these resources.3