A tiny, stocky parasitoid wasp, typically measuring around 0.9 -1.2 mm in length. Typically has a dark brown to black head and thorax. The abdomen is typically yellow, sometimes darkening toward the tip in males. Submarginal vein with only two setae. Brachyptery is also common in this group, particularly in males. Clava dark-tipped.
Possibly a species complex (further work required). 

Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

Parasitoid of aphids. 

Widely used as an aphid biocontrol agent, mainly in greenhouses.

Unknown.

Graham, M. D. V. (1976) The British species of Aphelinus with notes and descriptions of other European Aphelinidae (Hymenoptera). Systematic Entomology, 1(2), 123-146.