You stand in a garden. A low noise reaches your ears. You see a small insect flying near your head. You turn to look, and it flies out of sight. There it is again! You move slowly. You can see yellow and black stripes on it.
Is it a bee? It lands on a flower, and you take a closer look.
Bees fold(折叠) their wings onto their backs when they stop flying. But this insect' s wings reach out like a fly' s. That' s because it is a fly—a flower fly.
Many flower flies look like bees. This helps keep them safe from animals that may want to eat them. Insects with yellow and black stripes usually have stingers(刺). Insect eaters, such as some birds and frogs, need to get stung only once to know that stripes mean trouble. Flower flies can' t sting, but insect eaters see the stripes and leave the flies alone.
Flower flies spend most of their time looking for food. Like bees, flower flies eat pollen(花粉) and nectar(花蜜). This makes them easy to find in a garden full of flowers. They are helpful garden insects just like bees. Adult flower flies move pollen from one flower to another, which helps some flowers grow into fruit.
Flower flies can stay in one place while flying. Most insects move forward when they fly. But flower flies can twist their wings, much like hummingbirds do. Twisting keeps them in one place, so they can remain over flowers, leaves, or even you!
