A week or two back I came across this tiny (4mm long) yellow fly which reminded me of Pikachu. It is a frit fly (family Chloropidae, order Diptera), probably Thaumatomyia sp. but I can't be any more specific than that. (Some Thaumatomyia species were originally included in the genus Chlorops, and you will often find them referred to by that name out on the web.)
Photo taken in Reading University grounds, Reading, UK, on 2009-07-05.
This morning I went out again with the express intent of getting some more photos of the above flies and, although I thought did see one, it was too quick for me, and got away in the long grass. However, a bit later on I photographed the following similar looking fly:
It turns out that this is also a frit fly but this time in the genus Cetema, possibly Cetema ceris (the white arista, which are visible in the above photo, being one of the characteristics of that species). The red spot on the abdomen is probably a parasitic mite, the second mite I have come across on a fly in the past few days.
Photo taken in Reading University grounds, Reading, UK, on 2009-07-16.