Ore gray sandpiper
| Ore gray sandpiper | ||||||||||||
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Ore gray sandpiper |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Elaphrus aureus | ||||||||||||
| P. Müller , 1821 |
The Erzgraue Sandpiper ( Elaphrus aureus ) is a beetle from the family of ground beetles . The genus Elaphrus is represented in Europe with four subgenera and twelve species . Elaphrus aureus is included in the subgenus Elaphroterus .
The species is listed in the Red List of Endangered Animals in Germany, in Baden-Württemberg , in Bavaria , in North Rhine-Westphalia , and in Rhineland-Palatinate in category 2 (endangered). In the red list of ground beetles of the state of Brandenburg , the beetle is classified in category R (extremely rare). In Hesse, the species is rated as critically endangered and extremely rare .
Notes on the name
The beetle was described in 1821 by Ph. WJ Müller (also P. Muller) under the scientific name Elaphrus aureus . The Latin description begins with the indication of the color aeneo - subaureus ( Latin bronze to almost golden), which explains the species name aureus (Latin golden ). In the following description in German, the color of the upper side is characterized by Müller as a copper-reddish or brownish ore color , somewhat yellowish . This explains the German part of the name Erzgrauer . With the slight contradiction between golden and ore gray , it should be noted that the animals darken with age.
The generic name Elaphrus (from ancient Greek ελαφρός elaphrós, nimble) goes back to Fabricius . The name of the subgenus Elaphroterus derives from the old Gr . Comparative ελαφρότερος elaphróteros, more nimble from. The movement of Elaphrus aureus is particularly fast over short distances. The agility explains the German generic name Raschkäfer . Synonymous with the generic name Raschkäfer , the name riparian is common. He is referring to the fact that these ground beetles are found on the banks of rivers and streams.
The Elaphrus smaragdinus listed as a species by Reitter is only a color variant of Elaphrus aureus .
Characteristics of the beetle
  
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| Fig. 1: seen from the side, below, and in front | |||||||
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Fig. 2: Section of the wing cover with eye spots (round) and mirror spots (rectangular), horizontal: wing cover seam |
Fig. 3: Head from below, partially colored on the right : yellow: chin; red: lip button green: inner jaw button blue: outer jaw button |
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Fig. 4 A: Upper jaw from below; B: bristles on the trochanter of the 1st (above) and 2nd (below) pair of legs red drawn; C: bristle in the posterior corner of the pronotum (left corresponds to the front) |
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With a length of five to seven millimeters, the beetle is on average slightly smaller and narrower than Elaphrus riparius and thus the smallest Central European species of the genus. The basic tone of the color is coppery with a yellowish tinge. The purple color in the eye spots is not very spread out and only blurred. The green iridescent areas on the knees and tarsi, cheeks and antennae are silvery green. Most of the rails are translucent brownish. Overall, the beetle looks more colorful than the other species in the genus.
The head has noticeably large, protruding eyes on the sides. Behind this it is constricted and then widens again to the width of the front of the pronotum . The thread-like antennae are eleven and relatively short for ground beetles. The slightly convex upper lip in front shows a series of bristle-bearing points parallel to the front edge . The broad upper jaws are slightly asymmetrical, but basically built in the same way. They are about 1.5 times as long as they are wide and at the end they are curved inwards by about eighty degrees and sharply pointed. On the inside, at the base of the cutting edge, they have a so-called terebral tooth, below and further inside are several blunt, tooth-like elevations for grinding the food. In addition, a “brush” made up of a row of very short bristles can be seen (in Fig. 4A, left upper jaw from below). As is usual with ground beetles, the outer compartment of the lower jaw is designed as a second jaw probe. It is two-part (tinted green on the right in Fig. 5). The outer jaw button (tinted blue in Fig. 3 on the right) is four-part. The long lip buttons (tinted red in Fig. 3 on the right) are tripartite. The end link of the jaw button is cylindrical to spindle-shaped, the outer jaw button is trimmed, the end link of the lip button is long, slightly compressed and ends with an incline. The chin (tinted yellow on the right in Fig. 3) is three-toothed, the middle tooth is split.
The pronotum is clearly convex on the sides. The side edge is bulged, especially towards the base. The pronotum is a little more compact than that of Elaphrus ullrichi . A bristle (Fig. 4C), which is missing in Elaphrus ullrichi , arises in the back corner of the pronotum , which is hardly edged .
The elytra are the same width at the base of the pronotum, but then widen to double the width of the pronotum base to form pronounced shoulders. In the standard Joy-Harde-Lohse (see reference) they are called "hazelnut-shaped". Each wing cover has four rows of so-called eye points, which are interspersed with three rows of smooth mirror spots (Fig. 2). The level of the circular eye spots in the ore gray sandpiper does not differ significantly from its surroundings and is not surrounded by a wall as in Elaphrus uliginosus and Elaphrus cupreus . In their center the eye spots are blue-violet. The roughly rectangular mirror spots are shiny dark. On each wing cover there is a large mirror spot near the seam in front of the center, a smaller one behind it and a particularly large one behind it. There are also other mirror spots that are usually slightly raised above the surrounding level.
The underside of the front breast is bald and not hairy white as in Elaphrus riparius . The legs are moderately strong, the tarsi all five-limbed. In the males, not four, but only three limbs of the anterior tarsi are expanded. The number of bristle-bearing pore points on the trochanters of the two front pairs of legs is also taxonomically significant. In Elaphrus aureus there are two points on the trochanter of the foreleg (traced in red at the top in Fig. 4B), and only one such point (traced in red at the bottom in Fig. 4B) on the thigh rings of the middle pair of legs.
Characteristics of the larva
The elongated larva of Elaphrus aureus has three well-developed five-limbed pairs of legs, the end limb of which has a pair of claws with very short bristles. The larva is roughly seven times as long as it is wide. The head is rounded, the first part of the chest longer than it is broad. The transition from chest sections two and three to the abdominal segments is fluid. The two rear chest sections and the first eight abdominal sections are similar in plan and are all wider than they are long. The ninth and tenth abdomen segments are narrow. The ninth bears a pair of longer, slender appendages ( urogomphi ), which are undivided and with coarse bristles on the outside. They are longer than the concealed tenth abdomen segment and protrude far beyond the abdomen. Between them, the tenth segment of the abdomen is partially visible from above.
The head is not constricted at the base. He has three point eyes on each side. The front parts of the head skeleton are fused into a plate, the so-called nasal. The nasal ends in a sharp point in front. It is set off against the top of the head by a rudimentary suture in the shape of an upside-down Y. In Elaphrus aureus, this epicranial suture reaches about a quarter of the length of the base of the antennae and is therefore extremely short. The side of the head is slightly indented twice between the eyes and the rear edge of the head, the two indentations are roughly equally pronounced, the front not being noticeably longer than the back. The upper jaws are strong, directed forward and provided with a pointed tooth-like protrusion (retinaculum) on the inside. A large bristle sits on the outer edge just in front of the retinaculum. Inside, near the base, a group of short bristles forms a kind of brush. The base of the mandible is wide and protrudes inward from the apical part of the jaw. The inner ark of the lower jaw ( Lacinia ) has almost completely receded. The outer drawer is two-part. The four-part maxillary button arises from the outside. The first limb of the palpable jaw is the same length in the first larval stage, 0.8 times as long in the second larval stage and only 0.7 times as long in the third larval stage as the second maxillary palp limb. The four-part antennae arise laterally in front of the eyes and are no longer than the mandibles.
Further species-typical characteristics of the larva and differences between the three larval stages relate to the position and size ratios of different pores and bristles and the appearance of additional bristles. They are described in detail at Goulet.
biology
The beetle's typical biotope is formed by open and sparsely vegetated, but shaded soils near the water, in which willows are the predominant tree species. The species colonizes sandy to sandy-loamy subsoil formed by flooding. This habitat, which was once frequent, has declined significantly due to river straightening and the associated redesign of the banks as well as the expansion of agricultural areas to the banks. The populations have been fragmented as a result and their continued existence is threatened.
The adults are diurnal predators, the larvae are nocturnal and also have a predatory diet. The populations are relatively dense for predators. Studies in northern Germany revealed population densities between 2.2 and 5.9 individuals per square meter. But there are predatory beetle species that live in the bank area and have even higher population densities.
When examining the goiter contents, fragments of spiders were most frequently found, the remains of earthworms, beetles, crayfish, flies and butterflies were identified only as exceptions. However, only 52 individuals were examined, of which 32 had no content or no identifiable content of the goiter. Nevertheless, it is assumed that the species belongs to the generalists, since the mouthparts do not show any noticeable specialization for a certain group of prey.
In a study with 156 individuals, they all showed fully developed skin wings , but the wing muscles were mostly not or only slightly developed. The number of individuals with fully developed wings was less than ten percent. In Elaphrus cupreus and Elaphrus riparius , on the other hand, the flight muscles were usually fully developed. Recaptures of individually marked animals resulted in an exchange rate between different populations of only 3.3% with an average distance of 36.5 m, mainly downstream. The colonization of new suitable habitats is presumably only possible if they are directly adjacent to populated habitats, as statistically speaking, in contrast to related species, the animals have no flight ability and no flight records are mentioned in the literature.
The beetles appear in spring and reach their maximum activity in northern Germany, with strong local fluctuations between mid-May and the end of June. The first females with ripe eggs can be found from May onwards, and from mid-June the eggs of all examined females were already ripe. The number of individuals then drops dramatically. From July, animals of the new generation appear, which are initially recognizable by the lighter exoskeleton. The species then corresponds to the type of spring-breeding ground beetle. In the laboratory, the development time from egg to imago was measured in two individuals as 24 and 29 days, respectively; in nature, the development time is estimated at around one and a half months. This short development time is interpreted as an adaptation to a habitat shaped by flood events.
Hazard and protection
The species is clearly endangered on the one hand by the disappearance of suitable biotopes and on the other hand by its low ability to spread. In addition to protecting the habitats populated by the beetle, repopulation programs would be desirable in which animals are brought to suitable but unpopulated habitats under scientific supervision.
distribution
The species, which is predominantly native to Central and Eastern Europe, is found in western Europe from southwest France to the north of Central Europe. In the west and north their occurrence extends to the Netherlands , Germany and Poland . The northwestern edge of the distribution area is in Lower Saxony . In the south, the distribution extends from southern France to the Dalmatian coast. However, the species is absent in Albania and Greece . The distribution area extends far to the east and also reaches northern areas as far as Estonia . However, there is no evidence from Belarus . The beetle has been found furthest to the east in the Caucasus , but its occurrence there is isolated.
literature
- Heinz Joy, Karl Wilhelm Harde, Gustav Adolf Lohse: The beetles of Central Europe . tape 2 . Adephaga 1. Elsevier, Spektrum, Akad. Verl., Munich 1976, ISBN 3-87263-025-3 . P. 62
- Edmund Reitter : Fauna Germanica, the beetles of the German Empire, Volume I, KGLutz 'Verlag, Stuttgart 1908, p. 96
- Gustav Jäger (Ed.): CG Calwer’s Käferbuch . K. Thienemanns, Stuttgart 1876, 3rd edition p. 6
Individual evidence
- ↑ Elaphrus at Fauna Europaea. Retrieved January 5, 2016 and corresponding pages of the subgenera
- ↑ a b Elaphrus aureus in Fauna Europaea. Retrieved January 5, 2016
- ↑ Red List of Endangered Animals in Germany (Binot et alt. 1998) ( Memento of the original from March 1, 2016 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.
- ^ List of endangered ground beetles in Baden-Württemberg
- ^ List of endangered ground beetles in Bavaria
- ↑ Faunistic reports on selected ground beetle species in Westphalia as PDF
- ↑ List of endangered ground beetles in Rhineland-Palatinate ( Memento of the original from January 10, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Red list ground beetles of the state of Brandenburg
- ^ List of endangered ground beetles in Hessen
- ↑ a b c Ph. WJ Müller New insects in eds: Germar, and Zinken, called summer: Magazine of insects, 4th volume, Halle 1821, p. 229 Preview in Google book search
- ↑ a b Sigmund Schenkling: Explanation of the scientific beetle names (genus)
- ^ Henri Goulet: "The genera of holarctic Elaphrini and species of Elaphrus ..." in Questiones entomologicae 19, 219 - 482, 1983 as PDF
- ↑ a b c d e f Jens Guenther, Benjamin Hoelscher: "Distribution, population and food ecology of Elaphrus aureus in Northwest Germany" in Applied Carabidology 6 (2004) pp. 15-27 ISSN 1437-0867 as PDF
- ↑ Distribution map of Fauna Europaea ( memento of the original from January 10, 2016 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.
