This is the peak time of the year for various flying insects. It's the time when all the local wasps' nest populations peak, the gnats and midges plague us on summer walks, the sultry July and August weather brings out flying ants, and good conditions elsewhere in Europe may result in the migration of millions of moths, butterflies, dragonflies and ladybird beetles. (I am usually alerted to the ants' nuptial flights by the behaviour of birds. Not only the swifts, martins and swallows which live almost exclusively on flying insects, but also the noisy squadrons of gulls which pick the ants off both in the air and on the ground.)

One insect which sometimes causes needless concern is the 'marmalade fly' - a browny-orange and black creature about 10mm long belonging to the hover-fly family. This is a large family the members of which are found all over the world. Many of them, including the marmalade fly, have yellow or orange and black stripes. At first glance therefore they are often taken for wasps or bees. This is a big advantage for the fly, by mimicking the much more aggressive and dangerous wasp it fools its enemies. Add to this the fact that this is one of the migrating species, and that a few dozen can suddenly appear in the garden, and people too are fooled and fancy that they have an influx of wasps. This year I noticed that they suddenly turned up in my garden at the end of July.

Observing the flies for a few minutes will reveal the differences between them and wasps. As their name suggests they spend some of the time hovering close to flowers and generally have a less purposeful flight than wasps. The Americans call hover-flies 'flower flies' and flowers are all they are interested in. Wasps are hunters, finding aphids and other small insects to feed their grubs, hover-flies are just looking for a meal of pollen or honey. If you look closely enough you may also see that the flies only have one pair of wings whilst wasps have two pairs. In addition the male marmalade flies have large red eyes which meet on top of the head.

Whilst its numbers peak in the summer the marmalade fly is one of the few insects which may be seen at any time of the year and it is very good news for gardeners. Although the adult flies feed on flowers their larvae are, like others in this family, voracious predators of aphids.

Keep an eye out for this species and its cousins. Any yellow and black, or orange and black, insect which looks like a bee or a wasp, but is somehow different, not quite right, (doesn't have the right 'jizz' as birdwatchers would say) is most likely to be a harmless, indeed beneficial, hover-fly.