Suillia affinis is the European art of Heleomyzidae a small family of true flies in the insect order Diptera. Over 650 described species of Heleomyzidae occur in about 80 genera and 22 tribes distributed throughout the world; the greatest number occur in the Holarctic region. Around 100 species of Heleomyzidae are found in North America. Larvae feed on decaying plant and animal matter, mushrooms, and various fungi. All of the subfamilies have been commonly recognized as families in the past, but are now included within the Heleomyzidae.
Heleomyzidae are small to medium-sized flies which vary in colour from yellow to reddish yellow or reddish brown to black. The wings often have small but distinctly longer, well-spaced spines mixed with the shorter spines along the leading edge and the crossveins are often clouded.
Adults of Borboroides and Heleomicra are attracted to carcasses and faeces. The larvae of the Holarctic Suillinae and Tapeigaster occur principally in fungi. Larvae of Cairnsimyia live in borer tunnels in trees.