Fairyfly
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. These unusual-looking wings work by utilizing air resistance—which at their minuscule size is equivalent to moving through honey—so they sort of function as miniature paddles that swim through the air. 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 utilized as biological pest control agents. In a few unusual species, females are winged and leave the original host egg to find new hosts and deposit their eggs in them, while males are wingless, mate with their sisters, and die in the original host egg.
The fossil record of fairyflies extends from at least the Albian age of the Early Cretaceous.
Taxonomy
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.History
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.Earlier attempts of classification by Walker treated the group as a genus, and classified all other known fairyflies under it as subgenera. Walker later conceded to Haliday's classification in a letter in 1839 and requested assistance from Haliday in classifying the wasps collected by Charles Darwin on his voyage on. "Mymares", as well as other "tribes", were elevated to the family rank 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.
Etymology
The generic name Mymar was derived by Curtis from the Greek word μΰμαρ, an Aeolian variant of the standard Greek μῶμος.Classification
The Mymaridae are the most basal members of the superfamily Chalcidoidea. About 1,424 species of fairyflies are grouped in about 100 genera. Of the extant fairyfly genera, Eustochomorpha is the most basal. 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, but two proposals are notable. Annecke & Doutte proposed the subfamilies Alaptinae and Mymarinae based on the morphology of the gasters. Peck et al. proposed the subfamilies Gonatocerinae and Mymarinae based on the number of segments in the tarsi. Both systems included further tribal categories. A fossil subfamily was also proposed for a genus recovered from Canadian amber.
Description
Fairyflies are very small insects. They have body lengths from, typically. Their bodies are usually colored black, brown, or yellow, without the metallic coloration of some other wasps. 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. The antennal toruli are set high on the head and near the eye margins. They are separated by a distance of three to five times their own diameter. In contrast, the antennae of other chalcidoids are separated only by one diameter. In females, the antennae are tipped with club-like segments known as clava. In males, the antennae are filiform.File:Mymarilla wollastoni.jpg|thumb|left|Mymarilla wollastoni: Female exhibiting the extraordinarily densely hairy and domed forewings peculiar to the species. Close-up of the thread-like antennae of a male. Mymarilla wollastoni is endemic to the island of Saint Helena in the southern Atlantic. Scale bar = 1 mm
Most fairyflies possess wings with long bristles on the fringes. The forewings usually have hypochaeta. These are small bristles which point distinctly backwards on the ventral surface of the wing membrane.
Fairyflies exhibit considerable variation in their wing shapes in comparison to other chalcidoids. The fully developed wings of fairyflies are normally flat with rounded tips and are several times longer than they are wide. These kinds of wings usually exhibit interspecific and intergeneric variation in terms of the length to width ratio and the shape of the wing outline of the forewings. In some species the forewings are relatively wide, like in the genus Paranaphoidea which have forewings only two and a half times as long as they are wide. In other species, the forewings are extremely narrow, like in Cleruchus bicilliatus whose forewings are about thirty times as long as they are wide.
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.
The hindwings are stalked and very narrow. They do not exhibit much variation, in contrast to the forewings. They can range from narrow and thread-like to relatively wide. In rare instances, the hindwings may also exhibit curvature, with a convex or concave anterior and posterior margins.
Some fairyflies possess slightly reduced to greatly reduced wings, while others may even be completely wingless. Wing reduction or absence is usually exhibited by at least one sex of species that search for host eggs in confined areas. 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.
Because of their small sizes, fairyflies may sometimes be mistaken for members of the families Aphelinidae and Trichogrammatidae, but members of these other families can readily be distinguished by having much shorter antennae.
Distribution and habitat
Fairyflies are some of the most common chalcidoid wasps, but because of their minute sizes they are seldom noticed by humans. This apparent invisibility, their delicate bodies, and their hair-fringed wings have earned them their common name.Fairyflies are found in temperate and tropical regions throughout the world. The largest number of species can be found in tropical forests, with the greatest diversity of genera found in the Southern Hemisphere. In the Nearctic, only around 28 genera and 120 species are found.
Fairyflies can survive in all kinds of terrestrial habitats, from deserts to rainforests. At least five species are also known to be aquatic, inhabiting freshwater ponds and streams. 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.
Ecology
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. They do not seem to be species-specific when it comes to choosing hosts. Some species are known to parasitize insects from several families of a single order. Their most commonly observed hosts are insects belonging to the order Hemiptera, especially Auchenorrhyncha and Coccoidea, but this might be because these groups are simply better studied. Other important host orders include Coleoptera, Diptera, Odonata, Psocoptera, and Thysanoptera. 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. Their bodies are smaller than a single-celled Paramecium. 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 females of the species, however, are typical fairyflies, and are much larger. The smallest flying insect is also a mymarid, Kikiki huna from Hawaii, which is long.