Hermit (beetle)

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hermit
Hermit (Osmoderma eremita), female

Hermit ( Osmoderma eremita ), female

Systematics
Order : Beetle (Coleoptera)
Subordination : Polyphaga
Family : Scarab beetle (Scarabaeidae)
Subfamily : Rose chafer (Cetoniinae)
Genre : Osmoderma
Type : hermit
Scientific name
Osmoderma eremita
( Scopoli , 1763)

The hermit ( Osmoderma eremita ) is a beetle from the subfamily of the rose beetles (Cetoniinae), it is also called the Russian beetle . The rare and inconspicuous insect is listed in Annex II and IV of the Habitats Directive , a nature protection directive of the European Union, and classified there as a priority species , for whose species the community ... has special responsibility.

The generic name Osmoderma from Altgr. οσμή osmē, smell, u. δέρμα dérma, skin refers to the intense scent that surrounds the beetle. The species name eremita ( Latin eremīta, hermit) alludes to the fact that the species lives in tree hollows. The genus Osmoderma is represented worldwide with 12 species, two of which also occur in Europe. Osmoderma eremita lives in Europe in three subspecies. The western nominate form O. eremita eremita overlaps in Germany with the southeastern form O. eremita lassallei . The Eurofauna also has the subspecies O. eremita christinae . Another southern form O. eremita italica is under discussion. The relationships are still the subject of studies with rDNA .

features

This Latin text was the first description of the hermit by the Tyrolean naturalist Giovanni Antonio Scopoli in 1763 . He found him in a cave in a pear tree.

The feeler construction known from the cockchafer and dung beetles, the sturdy grave legs and the shape of the larvae known as grubs identify the hermit as a member of the superfamily Scarabaeoidea .

The beetle measures 23 to 39 millimeters in length and 14 to 19 millimeters in width, has an inconspicuous shiny brown-black color all over its body and has a faint metallic sheen. The head, thorax, and elytra are confused and partially wrinkled.

The head shield is widened and raised at the front (Fig. 1), then it tapers towards the point where the antennae deflect. It is also raised above this turning point and forms a hump there. The head shield is widest behind the antennae, where the hemispherical large compound eyes are located. A web of the head shield borders the eyes (Fig. 3). The forward-facing small upper jaws cannot be seen from above.

The ten-link antennae are short and clumsy. The first antennae is strong, long and club-shaped and has long hair (Fig. 3). The second antenna segment is significantly smaller and bulbous. The following antenna elements 3 to 7 are even smaller, close together and slightly thicken as a unit towards the antenna lobe. The antenna lobe is formed by the last three antennae segments. The penultimate link is extended to the front to form a flat oval disc, the two neighboring links close together and complement the disc to form a spindle. Its three parts, the so-called leaves of the antennae, can, however, be spread apart and are the seat of the olfactory organs . The antennae is shiny dark and covered with only a few long hairs.

The pronotum (Fig. 1) is only slightly wider at the head than it is, then, when curved outwards (convex), it quickly widens to about twice the width that it reaches before the center. Up to its base it tapers in a straight line and only slightly. At the base, the breast shield swings slightly outwards over almost the entire width, only a little inwards just before the clearly developed rear corners of the breast shield. It is only slightly arched and edged on the sides. In the middle it has a longitudinal furrow which is bordered on both sides by a bulge. Grooves and ridges are - like the humps on the head shield - more clearly developed in the males than in the females (sexual dimorphism, Fig. 1 and 2). On both sides of the bulges there are two weak cusps in front.

Osmoderma eremita head male.jpg Osmoderma eremita head female.jpg
Fig. 1: Males: clear humps
above the antennae, distinctive bulges
on the breastplate 		Fig. 2: Females:
humps on the head and bulges and
deepening of the breast shield flatter
Osmoderma eremita antenna bl.jpg
 Osmoderma eremita tibia front.jpg
Fig. 3: ten-segment antennae with a
three-leaved club
eye outlined by a bar 		Fig. 4: Top view of the rail of the
front leg
(training as a grave leg )
Osmoderma eremita stigma.jpg Osmoderma eremita tibia back.jpg
Fig. 5: Location of the spiracles on the
abdomen (white arrowhead) 		Fig. 6: Rail of the hind
leg from below
Osmoderma eremita larver.jpg Osmoderma eremita larva.JPG Osmoderma eremita mokkmm.jpg
Fig. 7: One- and two-
year-old larvae 		Fig. 8: Larva of the last
stage 		Fig. 9:
Feces on graph paper

The elytra are together about 1.5 times as wide as the base of the pronotum. They have well-developed shoulders and are also bulged on the outside at the back. However, these widenings only occur laterally, so that the wing covers are flat at the top. Part of the abdomen remains uncovered at the sides and behind. The unusually large scutellum is visible between the wing covers at their base . It is long pointed, triangular and has a shallow central furrow.

In the legs , the hips ( coxa ), thighs ( femur ) and splint ( tibia ) are strong, the splints are provided with teeth and thorns. In contrast, the tarsi , which are all clearly five-part, appear delicate. The middle and rear rails (Fig. 6) thicken towards the rear, at the end they are cut off abruptly and the sharp edge is drawn out to form spikes. The front rails have three flattened teeth on the outside that serve as shovels when digging (Fig. 4). Approximately opposite the end tooth at the tip of the anterior splint there is a strong thorn. The middle and rear rails have two strong thorns approaching each other near the point where the tarsi deflects; they can also have teeth on the outer edge, which can be pointed or receded (Fig. 6).

Six abdominal segments are visible from below. The front hips are cylindrical and protrude parallel to each other in the shape of a cone from the front chest. The middle hips are roughly perpendicular to the body axis. The back hips are almost touching. The spiracles of the abdomen are not located between the tergite and the sternite , but rather in the sclerotized and laterally raised sternites (Fig. 5).

biology

The beetles live in tree hollows, which they often never leave for their entire life. Their presence is linked to a scent that is produced by the males as a sexual attractant. It is described as “like Russian leather ” or “smelling of apricot”.

The males pose in the cave openings on hot days. In doing so, they release the characteristic attractant, which is said to be effective from 500 to 1000 meters. Mating takes place in the cave.

The females lay 20 to 80 eggs in the sludge of the trees, which is called black gauze, which is created with the help of large mushrooms that produce brown or white rot . The eggs are initially cloudy white, then they turn yellow, doubling in size and reaching a diameter of up to five millimeters. In the first larval stage, the larva is six millimeters long. It lives in the deeper, moist layers of the cave and eats the gauze near the cave wall, making the cave bigger. It also consumes the mycelium of the fungus that has attacked the tree, possibly improving its living conditions.

The larva (Fig. 7 and 8) needs three to four years to develop in Central Europe . In their third (last) stage, the larvae reach a length of up to 7.5 centimeters and weigh about 12 grams. Towards the end of development, in autumn they stick together sludge and excrement pellets to form a doll's cradle that is only smoothed on the inside. The excrement (Fig. 9) is up to seven millimeters long, smaller, identically shaped pieces of excrement come from other species of rose beetle that can live with the hermit. The overwintering takes place as a prepupa that can withstand cooling down to −8 ° C. After pupation in April / May, the imago hatches in May / June and breaks open the hard pupa cradle (pictures of larvae, pupa cradle and feces).

Depending on the number of animals and the supply of sludge, the hatched beetles remain in the cave or leave it, but this only occurs in around 15% of the animals. If there is a sufficient supply of muck, several hundred animals can populate the breeding tree. When the population density is high, animals migrate, and larvae cannibalism is also mentioned. The beetles are in the cave in or on the gauze. Their activity extends from morning to night, preferably in the afternoon and towards the evening. Although there are about as many males as females, the latter are more common outside the cave.

The animals only become active in flight on days on which 25 ° C or, according to other sources, 28 ° C are exceeded. However, differences in the activity pattern are to be expected within the distribution area. The beetles can then not only be found around the opening of the brood cavity, but also on flowers. They usually only move up to 200 meters from the breeding tree. The maximum flight distance is given as one to two kilometers, which is only possible if it is necessary to search for a new breeding tree. They fly from May to August, but mostly in July. The males only live two to three weeks, the females up to three months. Food is only consumed in exceptional cases.

Biotope and distribution

All suitable burrows in deciduous trees are accepted, with the amount of sludge available being more important than the type of breeding tree. Introduced tree species and even conifers like the yew and, in Greece, the Greek fir ( Abies cephalonica ) are reported as breeding trees. Preference is given to caves with more than 50 liters of sludge, which must have a sufficiently high level of moisture but not be too wet (greasy consistency). Cave-forming hardwood species such as B. the oak or in the south the plane tree are particularly common breeding trees. The animals like to choose caves at a higher height, 6 to 12 meters are given as a guide. If a tree collapses and the breeding cavity comes close to the ground, the osmoderma is quickly displaced by other animal species ( click beetles , earthworms , rhinoceros beetles ). For such caves, the trees must have reached a certain thickness and a certain age. The age of the tree is given as 150 to 200 years and the trunk diameter is 50 to 100 centimeters. This information is certainly influenced by the existing tree material. In Greece you can find the beetle in old plane trees with a significantly larger trunk diameter. On the other hand, thinner breeding trees are also reported. Pictures of breeding trees can be found on various websites.

A good breeding tree can be inhabited for decades, maybe even over a hundred years. The beetles in a tree are referred to as a population , the beetles in a contiguous range as a metapopulation . Since the strong fluctuations in the populations do not occur synchronously with one another, they usually do not affect the metapopulations.

The beetle's primary habitats are alluvial forest remains (hard and soft wood meadows) as well as oak and oak-hornbeam forests. It can be assumed that according to the extent of these riparian forests, the animal was originally widespread throughout Central Europe at lower and medium altitudes. Through the influence of humans, these habitats were transformed and cut up, so that the beetle moved to cemeteries, parks, avenues, orchards, etc. as secondary biotopes , which were created in its original area of ​​distribution. The sites known today are isolated. Thanks to the interest in this beetle at European level, they are well documented. In the future, all current data will be published on the Eremit-Net website.

The genus Osmoderma occurs in Europe, Near East and East Asia and in the east of North America, the species O. eremita only in Europe. It occurs only in places and not often, with a main distribution in Sweden and Spain . The beetle is rare in Germany, but is still widespread. The same applies to Austria. In Switzerland it is only found in the Solothurn area . The dwindling of its habitat can also lead to the local extinction of current occurrences. Across Europe (from 1990 to 2005) only 919 sites were reported.

Hazard and protection

Skeletal remains of osmoderma have been found in owl threads ; the insect is probably also eaten by other animals. Infestation by a nematode species is also fatal for the Russian beetle. Research clearly indicates that the decline in insect populations is anthropogenic (man-made). Among other things, renovation measures in parks and the displacement of near-natural forests by commercial forests deprive animals of the basis of life.

Osmoderma is protected in almost all countries by state and federal laws and at European level by the Habitats Directive and the Bern Convention . The species is listed as 2 (endangered) in the Red List of Endangered Animals in Germany. It was recognized that the hermit is representative of many xylobionts , especially saproxylophage species ( umbrella species ); With its monitoring , those are recorded at the same time and with its protection the living space of those is secured. The excrement is relatively easy to detect, the breeding caves are often not easily accessible, especially if they are located at great heights. They can also come from extinct populations. The guideline also recommends inspecting fallen, collapsed and felled trees in detail, searching owl vaults for remains of the beetle and searching the cave openings with binoculars on hot summer days.

According to the Habitats Directive, areas in which the animal occurs are to be designated as protected areas. In particular, the breeding trees must be protected. However, since the more suitable breeding trees are available, the better the preservation of the overall population is guaranteed, so even trees with caves that are not populated, even trees with rotten areas, would have to be protected as possible future breeding trees. This often results in contradictions to other legal regulations, such as path safety or traffic safety obligations . In order to preserve old trees, hiking trails might have to be diverted. Healthy cutting should have priority over felling. Larvae from felled trees should be transferred to other breeding trees. Suitable measures would also have to include future breeding trees in the planning and the areas for metapopulations enlarged as far as possible. Because of the beetles' love of warmth, the release of breeding trees is mentioned as a further measure, but this should be done carefully and care must be taken that the cave does not dry out. Development can still be completed in dead trees, but new generations can no longer survive there.

In the context of the political disputes about the new construction of the Stuttgart main station (" Stuttgart 21 "), the Juchtenkäfer gained public attention and notoriety since autumn 2010. The tree felling work in the middle palace garden also affected breeding trees of the Russian beetle. After the German railway had met through conservation of breeding trees, the species protection requirements, which raised Eisenbahnbundesamt end of January 2012 to the then accepted general Fällverbot for the remaining trees. In the nearby Rosenstein Park, a flora and fauna habitat (FFH), Deutsche Bahn also did not receive a felling permit for seven so-called Juchten beetle trees in October 2013. The opinion of the EU Commission required due to the occurrence in an FFH was received in February 2018, whereupon the Federal Railway Authority immediately issued a permit and the area was cleared.

literature

Web links

Commons : Hermit  - album with pictures, videos and audio files
Wiktionary: Eremit  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Systematics of beetles according to Wikipedia
  2. ↑ Directive 92/43 / EEC ( Memento of the original dated September 3, 2006 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / europa.eu.int
  3. ↑ Sigmund Schenkling: Explanation of the scientific beetle names (genus)
  4. ↑ Sigmund Schenkling: Explanation of the scientific beetle names (species)
  5. ↑ Systematics at BioLib
  6. ↑ Osmoderma in Fauna Europaea. Retrieved February 9, 2013
  7. ↑ Taxonomy
  8. ↑ a b c d e English work on Osmoderma (PDF; 905 kB)
  9. ↑ Article with comments on the first description of Osmoderma eremita
  10. ↑ Heinz Freude , Karl Wilhelm Harde , Gustav Adolf Lohse (ed.): Die Käfer Mitteleuropas . tape  8 . Teredilia Heteromera Lamellicornia . Elsevier, Spektrum, Akademischer Verlag, Munich 1969, ISBN 3-8274-0682-X .
  11. ^ Carl Gustav Calwer , Gustav Jäger (ed.): CG Calwer's Käferbuch . 3. Edition. K. Thienemanns, Stuttgart 1876.
  12. ↑ a b c d e Bavarian Species Handbook, p. 59 ff. ( Memento of the original from May 21, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 1.6 MB)  @1@ 2Template: Webachiv / IABot / www.lwf.bayern.de
  13. ↑ a b c State education server Baden-Württemberg
  14. ↑ a b Natura 2000 profile
  15. ↑ Brutbaum in France, text in French ( Memento of the original from September 30, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.indrenature.net
  16. ↑ Hermit net
  17. ↑ Federal Agency for Nature Conservation (Ed.): Red List of Endangered Animals in Germany. Landwirtschaftsverlag, Münster 1998, ISBN 3-89624-110-9 .
  18. ↑ Ralf Hoppe: Transverse aft column - Made in Braunschweig - how two Beetles make politics. In: Der Spiegel. No. 25, June 21, 2010, p. 54.
    Thomas Braun: Endangered species in the palace gardens: Railway protects beetles. on: Stuttgarter Zeitung , September 22, 2010. The
    court takes the side of the Juchten beetle. on: spiegel.de , October 14, 2010.
    Stuttgart 21: Federal Railway Authority confirms request for a report on preliminary investigations under     nature conservation law.  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. on the homepage of the Federal Railway Authority@1@ 2Template: Toter Link / www.eba.bund.de  
  19. ↑ Michael Gerster, Wolf-Dieter Obst: Railway meets species protection requirements. In: Stuttgarter Nachrichten. January 26, 2012.
  20. ↑ Michael Deufel: Stuttgart 21: Bahn has to leave seven trees in Rosensteinpark. In: Black Forest Messenger. October 22, 2013. Retrieved November 23, 2017 .
  21. ↑ Konstantin Schwarz: Bahn is allowed to fell Juchten beetle trees. In: Stuttgarter Zeitung. February 6, 2018, accessed February 16, 2018 .
  22. ↑ Trees near the Rosenstein tunnel are felled. In: Stuttgarter Zeitung. February 12, 2018, accessed February 16, 2018 .