Wasp

A female metallic green wasp, probably a Torymus sp (Hymenoptera: Torymidae), on knapweed (Centaurea sp).

Photo taken in the Wilderness, Whiteknights Park, Reading, UK, on 2013-08-18.

Hoverfly

A male Dasysyrphus albostriatus (Diptera: Syrphidae) on common fleabane (Pulicaria dysenterica).

Photos taken in Whiteknights Park, Reading, UK, on 2013-08-18.

Tephritid Fly

Acidia cognata (Diptera: Tephritidae) on a leaf of coltsfoot (Tussilago farfara), the host-plant for its larvae.

Photo taken beside the top lake, Whiteknights Park, Reading, UK, on 2013-08-18.

Hoverfly

From 4 years ago: a male Melangyna cincta = Melligramma cincta (Diptera: Syrphidae).  

For a female from last year see here.

Photo taken in Whiteknights Park, Reading, Uk on 2009-04-18.

Tachinid Fly

A male Cistogaster globosa (Diptera: Tachinidae) on wild parsnip (Pastinaca sativa).

See here for a female that I saw last summer.

Photo taken in Chazey Wood, near Caversham, UK, on 2013-08-11.