Smallest fly in the world as of yet: 0.4 mm only

[Palinurus]

Not really a 2D 'friend' maybe, but wonderful nevertheless.

From this website: _http://esa.publisher.ingentaconnect.com/content/esa/aesa/2012/00000105/00000004/art00005

Small Size No Protection for Acrobat Ants: World's Smallest Fly Is a Parasitic Phorid (Diptera: Phoridae)
Author: Brown, Brian V.
Source: Annals of the Entomological Society of America, Volume 105, Number 4, Pages 519-612 , pp. 550-554(5)

Abstract:

A new species of phorid fly, Euryplatea nanaknihali (Diptera: Phoridae), is described from Thailand. This is the first Oriental Region record for this genus; it is otherwise known only from the type species from Africa, where it parasitizes ants of the genus Crematogaster Lund. The new species is probably capable of parasitizing the smallest host Crematogaster (Formicidae) ants in its range. At 0.40 mm in body length, it is the smallest known fly in the world.

Keywords: Diptera; Phoridae; parasitoid; Thailand; smallest fly

DOI: _http://dx.doi.org/10.1603/AN12011

Publication date: 2012-07-01

Full article (PDF) here:
_http://docserver.ingentaconnect.com/deliver/connect/esa/00138746/v105n4/s5.pdf?expires=1341326128&id=0000&titleid=10263&checksum=E79EFB3D5BF0D6F6903EEF69BD5D0D06

Reconstruction of E. nanaknihali, with body size compared with a house fly, Musca domestica L.
To the left: ordinary housefly and tiny speck
To the right: Euryplatea nanaknihali enlarged many times

Edited to add:
Press release here: _http://www.entsoc.org/press-releases/do-worlds-smallest-flies-decapitate-ants