HOVERFLIES AND FLOWER FLIES

Helophilus pendulus on Michaelmas daisy.

Hoverflies, or flower flies, are one of the most important groups of pollinators of agricultural crops, fruit trees, and many flowers, despite the fact that they have no specific pollen-carrying structures. Their attractive black-and-yellow or orange coloration makes them beautiful additions to any garden. The colour schemes also mean they are often mistaken for wasps or bees, and this mimicry is a good defence against predators, which tend to avoid them for fear of being stung. In fact, hoverflies have no stinger. There are about 6,000 different kinds of hoverflies in the family Syrphidae. Like bees and butterflies, they practice complete metamorphosis, with four stages of the life cycle: egg, larva, pupa, and adult. Unlike the former, however, they have two wings, not four.

A hoverfly’s command of the air is incredible. As well as hovering, it can fly forward and backward, up and down. Its acceleration from a hovering start is simply breathtaking. The adults feed, mate, and lay eggs. They obtain energy-giving nectar and protein-rich pollen from flowers. Most prefer flowers in which the nectar and pollen are easy to reach, like umbellifers, thistles, and knapweeds. Some, however, have a long snout (rostrum), which they insert into more tubular flowers, such as red campions and bluebells. Others don’t visit flowers at all, but feed on the sugary secretions of aphids (honeydew) and pollen grains stuck to the surfaces of leaves. The larvae of some are predatory, feeding on other small invertebrates, such as aphids.