Most of these species inhabit particularly harsh and wind-swept environments, and the curvature may help in absorbing and retaining heat or prevent the fairyflies from being blown away.
They don't exhibit much variation, in contrast to the forewings.
They can be distinguished from other chalcid wasps by the H-shaped pattern of sutures on the front of their heads.
Fairyflies are some of the most common chalcid wasps, but are rarely noticed by humans because of their extremely small sizes.
The family Mymaridae was first established in 1833 by Irish entomologist Alexander Henry Haliday.
Haliday and two close friends and respected entomologists in their own right, John Curtis and Francis Walker, were influential in the early studies on Hymenoptera in the 19th century.
The largest genera are Anagrus, Anaphes, Gonatocerus, and Polynema, which comprise around half of all known species.