What is the smallest known insect?

The fairyfly is the smallest known insect. The record-holder is the male Dicopomorpha echmepterygis, a parasitic wasp measuring about 0.139 millimetres long.

Fairyflies belong to the wasp family Mymaridae, despite their delicate, almost magical common name. They are so small that their wings often resemble narrow structures fringed with hairs rather than the broad membranous wings seen on larger insects. Their tiny size also means that air behaves unusually viscously around them, making flight more like swimming through a thick fluid.

All known fairyflies are parasitoids: their larvae develop inside the eggs of other insects. In D. echmepterygis, the wingless males are especially reduced, lacking wings and functional eyes; they mate with females inside the host egg. The smallest flying insect is a different fairyfly, Kikiki huna, at about 0.15 millimetres. That distinction explains why “smallest insect” and “smallest flying insect” are not identical records.