Mymarommatidae
The Mymarommatidae are a peculiar family of minute Hymenoptera, presumably with parasitoid of life in insect eggs. Vilhelmsen and Krogmann called it " perhaps the most enigmatic taxon of wasps ." The described species about 15 are distributed worldwide. Approximately the same number of species have been found as fossils in amber.
Description
Mymarommatidae are tiny wasps between 0.3 and 0.8 millimeters in body length. They are distinctive by a number of morphological peculiarities. The head capsule of animals consisting of two separate parts, which are separated by a membranous interruption behind the mandibles. The rear part forms a perpendicular plate, the front part of the eye is hemispherical. Both parts can be pulled apart like an accordion, or be nested. But the latter may be an artifact that occurs only on dead animals. The mandibles of the animals are serrated on the outside, they gape so far apart that they can not be closed in life. The remaining mouthparts are rudimentary and functionless. It is believed that these structures serve the living animal to to liberate themselves from the egg case. By the bloated head, the mandibles were firmly pressed against the sheath, which could cut it so. The head also sit compound eyes from five to about 55 relatively large ommatidia, simple eyes ( ocelli ) can be present or absent. The sensors are ( kinked behind the long basal joint ) and towards significantly broadened in the female to the top geniculate ( culled ). They consist in the female, from nine to eleven, the male of twelve or thirteen segments. In the middle section ( mesosoma ) the pronotum is reduced and not visible from above. Also, the metanotum is reduced. The lateral portions of the central segment, the metanotum and propodeum which are fused to form a compact structure. The front wings are oval shaped and distinctly stalked, they are of short hair ( Mikrotricha ) covered. They have apparently no veins. On closer inspection, reinforcements are stem-like basal portion but visible, can be with a little imagination with the typical Flügelgeäder Chalcidoidea ( chalcid ) homologized. The hind wings are rudimentary and tiny, they only consist of a narrow and short flap, which has kneifzangenartig bristles arranged at the end of two. Thus, they are fixed to the living animal with the fore wings. Strikingly, this is the membrane of the wing not continuous, but microscopic observation has a distinctly reticulated structure, such a mode of formation is unique within the Hymenoptera. The legs have, as widely used in the Legimmen, a two-part ring thigh ( trochanter ), so a seemingly extra leg member, the Trochantellus on. The spurs on the rails ( tibiae ) are reduced to a single of the Vordertibien. The Mymarommatidae the free abdomen sitting at mesosoma with a petioles ( petiole ), which consists of two clearly discernible segments. This mode of formation is also unique in the ( recent ) Hymenoptera. The remaining free abdomen (or gaster ) is large and smooth tergites and sternites covered that engage imbricated. It consists of six segments. The ovipositor ( ovipositor ) of the females is hidden in the rest position in the abdomen. In use, the abdomen tip is probably abducted and rotated the ovipositor, it is then not used to the rear, but on the ventral side.
Dissemination
The family is distributed worldwide. Certificates are also of isolated oceanic islands, including the Hawaiian Islands, and several sub-Antarctic island groups before. In Europe, only one species is known: Mymaromma anomala. The species was also found in Germany.
Way of life
The lifestyle of Mymarommatidae is unknown. By no way are any observations on living animals or evidence of developmental stages. This is perhaps not surprising given the size of the animals. All editors suggest, however, that they develop as parasitoids of insect eggs inside. Some researchers are trying to suggest in a kind of circumstantial evidence that the most likely hosts eggs of dust lice ( Psocoptera ) are. The wasps are found in the summer months, the long observation period suggests the existence of several generations close. The at least initially, very rare find density is certainly methodically conditioned to a large extent. The best evidence is obtained with yellow pan traps, then even a kind that has been designated ( Mymaromma ytp, of Engl. Yellow pan trap ).
System
The Mymarommatidae be due to the numerous morphological peculiarities in its own superfamily, the Mymarommatoidea led. The first editor and explorer suspected that the animals belong to the Mymaridae ( dwarf wasps ), another family of tiny Hymenoptera that parasitize insect eggs. This has not been confirmed. The superfamily belongs to a lineage of Hymenoptera, which consists mainly of species with very small body size, the Proctotrupomorpha. This also known as " Mikrohymenopteren " combined groups are very diverse, but extremely poorly researched. Sister group of the Mymarommatoidea are most likely the jewel wasps ( Chalcidoidea ). This grouping was set up based on morphological characteristics, it is also supported by molecular studies.
The taxonomy of Mymaromatidae was up to the monograph by Gibson et al. confused. All extant species were sorted into the genus Palaeomymar, which was compiled on the basis of a fossil species.
Today, the following genera are recognized:
- Mymaromma,
- Mymaromella,
- Zealoromma, 2 species from New Zealand
Fossil record
Fossil Mymarommatidae are relatively numerous before, exclusively as inclusions ( inclusions ) in amber. Evidence is there from almost all significant amber deposits. Many findings were not published until after 2000. The family exists at least since the Cretaceous. Some of the Cretaceous finds are an extinct second family assigned ( genus Galloromma, family Gallorommatidae ). The problem is the position of the Serphitidae, a likewise extinct family. The Serphitidae were usually significantly greater with rich Flügelgeäder, the only other group but also showed them on a dual-segment petiole. While previous editors held a context for very speculative and this feature regarded as a possible homoplasy, fossils have been found, which can be well interpreted as a possible transitional forms now. Perhaps the Serphitidae are thus the core group of Mymarommatidae. If confirmed, then the common superfamily would have to be called from priority reasons Serphitoidea.