Fairyflies are tiny wasps that are egg parasitoids belonging to the Chalcidoidea, are non-metallic, 0.2 - 4.0mm in length and have a global distribution. Their family Mymaridae includes Alaptus magnanimus (0.21 mm., male), the smallest discovered species in the class Insecta. Fairyflies can be found at great altitude, their small size leading to easy dispersal by wind currents. The largest of fairyflies have a wingspan of 3mm.
Fairyfly females are larger than male fairyflies and are also much better at flying than the males. Many species swim submerged under the water using their wings as paddles. Mating and egg laying may also occur underwater. An individual of these genera of fairyflies can stay underwater for up to 15 days. To exit the water, they climb onto a the stem of a plant that breaks the surface.
There are 1401 species of fairyfly and 100 genera. No commonly accepted sub-family been has acknowledged. When collected correctly fairyflies are the most common wasps. Common hosts of fairyflies include the eggs of crickets, grasshoppers, beetles, true bugs, cicadas, aphids, lice, flies and aquatic bugs. Cicada eggs are the most common hosts. Pupation takes place inside the host egg shell. Successful bio-control programs have been launched using fairyflies to parasitise insects feeding on Eucalyptus species. Notable programs have occurred in southern Europe, South Africa, South America, New Zealand and North America. Fairyflies could be a common and helpful parasite in many eco-systems. Fairyflies are difficult to collect, and thus, not surprisingly, little is known about them. This is an area of entomology where an amateur naturalist could make a significant difference.