Right, and below are hover flies (family Syrphidae). There are 6 000 species world wide. Note the the aristate antennae and huge eyes typical of the more "advanced" flies. Adult hover flies feed on pollen and nectar, and many are mimics of bees and wasps. Many Hover fly larvae are slug-like and eat aphids (see below left), others are scavengers.

Below left is mate seeking behaviour. The male hoverfly generally has two strategies in seeking a mate. 1) He patrols around oviposition sites. The female will have already mated if she is seeking a site to lay eggs. But if the male can persuade her to mate again his sperm will have precedence. 2) He patrols over flowers. This is shown above. He will investigate anything that remotely resembles a female hoverfly bouncing down to get close or even touch the insect. Mating is rarely seen. Hoverflies are valuable pollinators

On the left is an aphid-eating hoverfly larva. Note the pointed head-end.

The African water lily on its first day of blooming has hundreds of showy stamens and a nice bright flower. This attracts hover flies. On day 1 in the centre of the flower is a pool of poisonous liquid that looks like nectar. When the hover fly lands on the stamen it falls into this liquid as the stamen are very smooth and overhangs the pool. The hover fly cannot climb out as there is nothing to get a grip on. So the hover fly dies in the poisonous liquid. At night the flower closes and the liquid washes pollen from day two water lilies off the body of the dead hover fly. This pollen fertilises eggs at the bottom of the liquid. On day two it is quite safe for hover flies to visit the lily as the stamens no longer hang over a poisonous pool as the pool has gone. The hover flies will gather pollen on their bodies, but will pay with their lives if they then try to do the same to a day one flower.

On the left is Piophila casei, the cheese fly, in the Piophilidae family. The larva are called cheese skippers or hoppers. They get this name because when disturbed they can flex their bodies to cause them to jump as much as 15 cm.

Drosophilidae family
These are commonly known as the fruit flies and vinegar flies. They are found world wide, and there are around 1500 species in the world and 50 British species. All are small, brown, grey or yellow flies, often with brightly coloured eyes. On the left is a typical adult fly. They feed on decaying and/or fermenting plant materials. They are commonly used in genetic studies as they have large chromosomes easily obtainable from the salivary glands, and they have a very short life cycle.