|Sixteen different species of hoverfly|
As their common name suggests, they are often seen hovering or sucking nectar at flowers. The adults of many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods.
In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or in ponds and streams. In other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects.
Aphids alone cause tens of millions of dollars of damage to crops worldwide every year. Hoverflies are important natural enemies of these pests, and can be used in biological control. Some adult syrphid flies are important pollinators.
Hoverflies are harmless to most other animals despite their mimicry of the black and yellow stripes of wasps. They are a classic example of Batesian mimicry. The Batesian mimic is a sheep in wolf's clothing: it looks like something dangerous or which tastes disgusting, but in reality it is good to eat. Hover flies look roughly like little wasps, and their warning colouration is well-known to birds.