Agathidium

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Agathidium
Agathidium mandibulare

Agathidium mandibulare

Systematics
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Subordination : Polyphaga
Family : Leiodidae
Subfamily : Sponge Ball Beetle (Leiodinae)
Genre : Agathidium
Scientific name
Agathidium
Tank , 1797
Agathidium varians on a branch. (Video, 1m 36s)

Agathidium is a genus of beetles in the Leiodidae family. Within the subfamily Leiodinae , Agathidium belongs to the Agathidiini tribe.

features

The beetles of the genus Agathidium are very small, they reach a length of one to six millimeters. The color ranges from red-brown to dark brown to black, and noticeable colors are only rarely represented. Many species of the genus are flightless. The wing covers and pronotum are shiny and mostly punctured. The points are arranged irregularly or occasionally in rows. If the beetles are covered by fungal spores, it is extremely difficult to see them, even in the laboratory.

The species of the genus Agathidium , like the other members of the Agathidiini tribe, have legs, in contrast to the sponge-ball beetles compiled in the Leiodini tribe, which have grave legs.

Spherical shape

Their back shield and pronotum are usually strongly arched, but there are also elongated oval types. Some types, e.g. B. Agathidium fawcettae , can curl up into an almost complete ball. In this position the legs are drawn in and the antennae are hidden in their own grooves on the underside of the head. The broad side edges of the pronotum overlap the edges of the wing covers so that the entire body is protected.

Asymmetrical horn formation in males

The males of some species, e.g. B. Agathidium difforme and Agathidium pulchrum have a horn-like extension on the left mandible , which is used to drive away male rivals. Other sex differences in some species are the broad first tarsi links of the front and middle pairs of legs of the males or a tooth-like formation on the thighs of the hind legs.

Habitat and way of life

Similar to the related genus Anisotoma , the species of the genus Agathidium specialize in slime molds (Eumycetozoa). They live on and from the slime mold. The beetle's habitat is therefore where the slime mold can develop: under bark, on decaying wood or in the leaf litter of the forests. Like the slime mold, the beetles of the genus Agathidium are distributed worldwide, but they are mainly found in the northern hemisphere, where they occur from the forests of the temperate zone to the tropical rainforests of the montane altitude .

Slime mold as a food source

The affinity of the genus Agathidium the slime molds becomes clear when they are in the vicinity of the Sporocarp designated spore-forming fruiting bodies reside. Due to the development of the mandibles of some Agathidium species, it is assumed that they break down the spores of the slime mold and use them as a source of food. The main food of the beetles could also be the plasmodial stages of the slime molds, if the amoeba-like unicellular organisms temporarily form an organizational form that moves on the ground like a tough, slimy mass. Individual beetles could be observed on such plasmodia both in the laboratory and in nature . Often, however, the slime molds are difficult to detect because of the small size of the unicellular organisms and their hidden way of life.

The slime molds on which Agathidium species can be found include almost all species of the real slime mold ( Myxogastria ), including the nearctic genus Physarum , the species Brefeldia maxima and the species of the genus Fuligo with the yellow tufted flower ( Fuligo septica ).

Stand mushrooms as a substrate

The beetles of the genus Agathidium can therefore be found in nature without a clear association with slime molds, e.g. B. on various stand mushrooms , which also include a number of tree mushrooms and the well-known cap mushrooms . However, it has not yet been finally clarified whether the beetles can feed themselves directly on these mushrooms or whether they graze on slime molds that live on the rotting fruit bodies of the mushrooms. For Agathidium aristerium it is sufficiently clear that it feeds on the slime mold Physarum polycephalum , which is often found on the fruiting body of the oyster mushroom ( Pleurotus ostreatus ). Conversely , spores of this fungus have been found in the digestive tract of Agathidium seminulum , a species of beetle that can be found on the scaly porling ( Polyporus squamosus) . This suggests a diet straight from the mushroom's fruiting body. What role the genus Agathidium plays in the spread of the spores of the slime mold or the mushroom mushrooms is still unclear.

Taxonomy and nomenclature

The genus Agathidium was first mentioned in 1797 by Georg Wolfgang Franz Panzer in his work Faunae insectorum Germanicae initia, or Germany's insects .

Naming after people

It is noticeable that many recently described beetle species from the genus Agathidium have an eponym in the scientific name, i.e. that is, they are named after a well-known personality. Agathidium bushi , cheneyi Agathidium , rumsfeldi Agathidium and Agathidium vaderi are species which of the two former Cornell - Entomologists Quentin D. Wheeler (after a stay at the Natural History Museum in London since 2006 at the Arizona State University ) and Kelly B. Miller ( now at Brigham Young University ) were named after George W. Bush , Dick Cheney , Donald Rumsfeld , and Darth Vader , respectively.

Selected species

In Europe there are around 100 species of the genus Agathidium from 4 subgenera. There are more than 350 species in the Orientalis , a fauna kingdom in the great biogeographical region of Palaeotropic . It is to be expected that many species that have so far been ignored due to the small size of the beetles will be discovered and described.

In 2005, Kelly B. Miller and Quentin D. Wheeler examined the North and Central American species groups around Agathidium concinnum , Agathidium pulchrum , Agathidium compressidens , Agathidium iota , and Agathidium oniscoides and described 58 new species. When naming the numerous species, members of the then government of the United States as well as wives, an employee and states of the USA and Mexico were taken into account.

  • Agathidium assimile Fall, Agathidium municeps Fall and Agathidium falli Hatch were synonymous with Agathidium angulare Mannerheim ;
  • Agathidium alticola Fall is now a synonym of Agathidium athabascanum Fall;
  • Agathidium contiguum Fall, Agathidium varipunctatum Hatch and Agathidium striolum Hatch are more recent names for Agathidium picipes Fall;
  • Agathidium californicum Horn and Agathidium alutaceum Fall are synonyms of Agathidium exiguum Melsheimer.

supporting documents

Individual evidence

  1. ↑ a b c d e f Kelly B. Miller & Quentin D. Wheeler: Slime-mold beetles of the genus Agathidium Panzer in North and Central America, part II. Coleoptera: Leiodidae . Bulletin of the American Museum of Natural History, 291, 1, pp. 1–167, 2005 doi : 10.1206 / 0003-0090 (2005) 291 <0001: SBOTGA> 2.0.CO; 2 PDF
  2. ↑ a b Atlantic Canada Coleoptera: Agathidium Panzer 1797 and Gelae Miller and Wheeler 2004 (with pictures)
  3. ↑ Kelly B. Miller & Quentin D. Wheeler: Asymmetrical male mandibular horns and mating behavior in Agathidium Panzer (Coleoptera: Leiodidae). Journal of Natural History, 39, 10, pages 779-792, 2005
  4. ↑ Agathidium in European beetles, identification key

literature

  • Quentin D. Wheeler, Kelly B. Miller: Slime-mold beetles of the genus Agathidium Panzer in North and Central America, Part I. Coleoptera: Leiodidae . In: Bulletin of the American Museum of Natural History . No. 290 , March 24, 2005, ISSN  0003-0090 ( amnh.org [PDF]).
  • Quentin D. Wheeler, Kelly B. Miller: Slime-mold beetles of the genus Agathidium Panzer in North and Central America, Part II. Coleoptera: Leiodidae . In: Bulletin of the American Museum of Natural History . No. 291 , March 24, 2005, ISSN  0003-0090 ( amnh.org [PDF]).

Web links

Commons : Agathidium  - collection of images, videos and audio files