Fairyfly

Family of wasps

The Mymaridae, commonly known as fairyflies or fairy wasps, are a family of chalcidoid wasps found in temperate, subtropical, and tropical regions throughout the world. The family contains around 100 genera with 1,400 species. Fairyflies are very tiny insects, like most chalcidoid wasps, mostly ranging from long. They include the world's smallest known insect, with a body length of only , and the smallest known flying insect, only long. They usually have nonmetallic black, brown, or yellow bodies. The antennae of the females are distinctively tipped by club like segments, while male antennae are thread like. Their wings are usually slender and possess long bristles, giving them a hairy or feathery appearance, although some species may have greatly reduced stubby wings or lack wings altogether. They can be distinguished from other chalcidoids by the H shaped pattern of sutures on the front of their heads. Fairyflies are among the most common chalcidoids, but are rarely noticed by humans because of their extremely small sizes. Their adult lifespans are very short, usually only a few days. All known fairyflies are parasitoids of the eggs of other insects, and several species have been successfully used as biological pest control agents. The fossil record of fairyflies extends from at least the Albian age (about 107 myr) of the Early Cretaceous.

The family Mymaridae was first established in 1833 by Irish entomologist Alexander Henry Haliday. Haliday and two close friends, John Curtis and Francis Walker, respected entomologists in their own right, were influential in the early studies of Hymenoptera in the 19th century.

Haliday originally described fairyflies as the tribe "Mymares" of the family "Chalcides". He based his descriptions on the type genus Mymar, described by John Curtis in 1829. "Mymares", as well as other "tribes", were elevated to the family rank (as Mymaridae) by Haliday in 1839. Haliday described fairyflies as "the very atoms of the order Hymenoptera" and remarked on the beauty of their wings when viewed under the microscope. These characteristics of fairyflies also made them popular to entomologists and microscopists of the late 19th and early 20th centuries. The beautifully mounted fairyfly specimens of the early 20th century English microscopist Fred Enock are possibly the most famous of the collections.

The generic name Mymar (and by extension, Mymaridae) was derived by Curtis from the Greek word μΰμαρ (mymar), an Aeolian variant of the standard Greek μῶμος (mōmos, "spot" or "blot"). About 1,424 species of fairyflies are grouped in about 100 genera. The largest genera are Anagrus, Anaphes, Gonatocerus, and Polynema, which comprise around half of all known species. They are the most commonly encountered fairyflies, followed by Alaptus, Camptoptera, Erythmelus, Ooctonus, and Stethynium, which make up a further quarter of known species. The Mymaridae are considered to be monophyletic, but their exact relationships with other chalcidoids remain unclear. No commonly accepted subfamilies have been acknowledged, A fossil subfamily was also proposed for a genus recovered from Canadian amber. They can be distinguished from other chalcidoids by having an H shaped pattern of sutures, known as trabeculae or carinae, below the frontmost ocelli and the inner eye margins. Rarely, the sutures can also extend behind the ocelli. Fairyflies have long antennae, at least as long as the head and the mesosoma (middle part of the body). In females, the antennae are tipped with club like segments known as clava. In males, the antennae are filiform (thread like). Forewing curvature, such that it is distinctly convex or dome shaped, is also exhibited by at least one species of the genera Cremnomymar, Mymarilla, Parapolynema, and Richteria. 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. Wing reduction or absence is usually exhibited by at least one sex (usually the female) of species that search for host eggs in confined areas (like leaf litter, soil, or the tubules of bracket fungi). Wing reduction or absence is also exhibited by species that inhabit windy habitats like oceanic islands or high elevations, particularly endemic species which are found in isolated habitats or are located far from the nearest mainland. In these habitats, wings would only be a hindrance to the fairyflies, so are strongly selected against in evolution. For example, the three known species of fairyflies found in the far southern islands of Campbell and Auckland of the southwestern Pacific and South Georgia of the southern Atlantic, as well as 20% of the fairyfly fauna in the Juan Fernández Islands, Norfolk Island, and Lord Howe Island, are all wingless or short winged. While wingless and short winged species may also be found in islands near continents and in continental habitats, they usually constitute only a small percentage of the overall number of species. Among these is Caraphractus cinctus, which uses its wings as paddles to swim. They can remain underwater for as long as 15 days. Because of their small sizes they have to exit the water by climbing up plant stems that jut through the surface, as they would not otherwise be able to break the surface tension of the water.

All known fairyflies are parasitoids of eggs of other insects. These eggs are commonly laid in concealed locations, such as in plant tissues or underground. but this might be because these groups are simply better studied. Other important host orders include Coleoptera (beetles), Diptera (true flies), Odonata (dragonflies and allies), Psocoptera (booklice and allies), and Thysanoptera (thrips). Hosts are known definitely for only a quarter of known genera. Fairyflies include the smallest known insect, Dicopomorpha echmepterygis from Illinois, whose males are only long. They do not have wings or eyes, their mouths are mere holes, and their antennae are simply spherical blobs. The ends of their legs form suction cups with which they hold on to females long enough to fertilize them. Four males, lined up end to end, would just about encompass the width of a period at the end of a typical printed sentence. The smallest flying insect is also a mymarid, Kikiki huna from Hawaii, which is long.

Very little is known of the life histories of fairyflies, as only a few species have been observed extensively. Adult lifespans of fairyflies are very short. After emerging, females search rapidly for suitable host eggs by tapping their antennae over stems or barks of plants. When a telltale scar left by egg laying insects is found, a female will insert her antennae into the recess and check to see if the eggs are suitable. If they are, she will thrust her ovipositor into all of the eggs and lay her own eggs inside in quick succession. She retains contact with each of the eggs with her antennae while doing this. Metamorphosis occurs completely within the host egg. They are especially valued for their ability to locate the eggs of their hosts. They have also been shown to be capable of overwintering in prune leafhoppers (Edwardsiana prunicola). Gonatocerus triguttatus, Gonatocerus tuberculifemur, and Anagrus epos (which is probably a species complex) were also studied for possible use in controlling glassy winged sharpshooters (Homalodisca vitripennis) in California. Gonatocerus triguttatus and Gonatocerus ashmeadi were eventually introduced in California in 2000. It proved to be very successful, causing about a 90% decline in populations of glassy winged sharpshooters. In 2005, Gonatocerus ashmeadi was used against invasive glassy winged sharpshooters in Tahiti and Moorea of the French Polynesia. Again, it was very effective, bringing down the pest density by about 95% in just a year after introduction. It was subsequently also released in the Society Islands, the Marquesas, and the Austral Islands, where similar results were obtained against glassy winged sharpshooters. In South Africa, Anaphes nitens was introduced very successfully to control an undescribed species of eucalyptus snout beetle (Gonipterus sp. ).

Fairyflies are well represented in fossil amber inclusions, copal, and compression fossils. Their fossils have been found from the Early Cretaceous up to the Miocene epoch. It is, in fact, the only family of chalcidoids definitely known to date back to the Cretaceous period. Cretaceous fairyflies are much rarer. In 1975, Carl M. Yoshimoto described four genera of fairyflies from the Cretaceous of Canada. In 2011, John T. Huber and George Poinar Jr. described the genus Myanmymar from Burmese amber. Dating back to the Lower Cenomanian age (about 100 mya) of the Late Cretaceous, it is the oldest known fairyfly (and chalcidoid). They are surprisingly very similar to modern genera, though with a greater number of flagellar segments and longer forewing veins. The characteristics of the fossil (taking into account Yoshimoto's earlier discoveries) led them to conclude fairfylies either may have existed much earlier than Myanmymar, or they may have diversified rapidly during that time period. Allomymar and Metanthemus has been transferred to the family Aphelinidae. The fossil genus Protooctonus has been transferred to the family Mymarommatidae, and is now considered to be a synonym of Archaeromma. Nesopolynema, Oncomymar, and Scolopsopteron were synonymized to the genus Cremnomymar in 2013, and their species are now classified under the latter. Genera marked with † are extinct.

Despite their relative abundance, fairyflies are unpopular among modern insect collectors because of the great difficulty in collecting them. As one of the least known insect families, a large amount of information is still waiting to be discovered about fairyflies. Blockquote|The minute Hymenoptera are best collected by beating into, and sweeping with, a net made of fine gauze, and Mr. Haliday recommends me to collect them in quills, and afterwards to empty their contents into hot water, by which means their wings are naturally expanded; then by introducing a card under them to take them out of the water, arranging the legs and wings when necessary with a camel's hair pencil, and leaving them upon the card till they are dry, they may afterwards be taken off with a penknife, and gummed upon the points of small pieces of drawing or card paper of a long triangular form.|John Curtis|source= British Entomology Vol. 7 (1830)

Rearing is also another method that can bring the most rewards. This can be done with wild host eggs or laboratory prepared host eggs that are exposed in suitable habitats outside. They can then be taken in after a sufficient amount of time has passed and examined for developing fairyflies. With this method, it is possible to observe the life history and determine the hosts of particular species of discovered fairyflies.