Two More Species of Thistle Gall Fly

On a thistle (Cirsium sp) in one of the few remaining areas of grassland that hasn't been mown yet: gall fly Anomoia purmunda (Diptera: Tephritidae). When I first saw it, I thought it was two aphids standing on the back of a fly, and was quite surprised when the whole 'assemblage' flew off as a single unit. 

A few metres away I came across the following, also on a thistle:

Probably Terellia ruficauda (Diptera: Tephritidae).

Photos taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2010-07-11.