Fairyflies

Definition

Common name for the family Mymaridae, a group of minute chalcidoid wasps (Hymenoptera) that includes some of the smallest known insects. Adults typically range from 0.5–5 mm in body length, with several species measuring under 0.2 mm; many possess reduced wing venation and some species are entirely wingless. The family comprises approximately 100 genera and 1,400 described species distributed worldwide in temperate, subtropical, and tropical habitats. Fairyflies are parasitoids, primarily attacking the eggs of other insects—especially Hemiptera, Coleoptera, and Odonata—making them significant biological control agents.

Etymology

From 'fairy' (alluding to their diminutive, delicate appearance) + 'fly' (in the older sense of any small winged insect), with the singular 'fairyfly' patterned after 'butterfly.'

Example

The fairyfly *Kikiki huna* from Hawaii measures roughly 150 micrometers in body length, smaller than many single-celled protists and the smallest known flying insect.

Synonyms

• fairy wasps
• Mymaridae

Related Terms

• chalcidoid wasps
• Parasitoid
• Biological control
• microhymenoptera
• egg parasitoid
• Mymaridae

Usage Notes

The term 'fairyflies' refers specifically to the family Mymaridae, not to true flies (Diptera). Specialists generally prefer 'fairy wasps' or the family name Mymaridae to avoid confusion. The singular form 'fairyfly' is patterned after 'butterfly' rather than following regular English morphology. Size claims require care: while fairyflies include the smallest known insects, not all species are extraordinarily minute, and wingless forms can be difficult to distinguish from other microhymenoptera in field samples.