Hoverflies dress like wasps but spend their days pollinating flowers and eating aphids
That striped insect hanging motionless over your garden is probably no wasp at all. Many of the roughly 6,000 hoverfly species copy the colours of stinging bees and wasps, a bluff that may deter predators, yet they are harmless to most mammals and rank as perhaps the second most important pollinators after wild bees.
Hovering is how they got the name, but unlike hummingbirds they do not feed in mid-air. Males hold position as a territorial display while looking for mates, and females hover to inspect places to lay eggs. Sizes range widely, from Paragus tibialis at 3 to 5 millimetres to Criorhina nigriventris at over 20. Most can be told from other flies by a spurious vein running parallel to the fourth main vein of the wing.
Adults live on nectar and pollen and show a repeated preference for white and yellow blooms, often choosing open flowers suited to their short mouthparts. Some are fussy: Cheilosia albitarsis seems to visit only creeping buttercup. Plants exploit these habits. One orchid, Epipactis veratrifolia, imitates the alarm scent of aphids to lure hoverflies, while a slipper orchid in southwest China fools them with its yellow colour. Bees may carry more pollen per trip, but flies may make up for it with more visits.
The larvae are far less picky eaters. Some consume rotting matter, others hunt aphids, thrips and leafhoppers, which makes them useful for biological pest control; gardeners plant yarrow, chamomile, parsley or buckwheat to attract them. The rat-tailed maggot of the drone fly breathes through a rear siphon while living in stagnant water, and is even sold as ice-fishing bait. Some species lodge in bumblebee nests, and others with ants.
Found on every continent except Antarctica, hoverflies have a fossil record stretching back through Eocene deposits and Baltic amber. The Swedish writer Fredrik Sjöberg, in The Fly Trap, describes collecting 202 species over seven years on the Baltic island of Runmarö, 180 of them in his own garden.
Source: Hoverfly
