Onthophagus taurus
| Onthophagus taurus | ||||||||||||
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Onthophagus taurus , male with reduced horns |
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| Onthophagus taurus | ||||||||||||
| ( Schreber , 1759) |
Onthophagus taurus (also bull's head dung beetle ) is a Dungkäferart from the family of scarab beetles (Scarabaeidae).
The generic name Onthophagus from Greek ὄνϑος 'onthos' and φάγος 'phagos' means 'dung eater'. The specific epithet taurus is the Latin word for bull and was chosen because of the horn-like protrusions in some males of this species.
features
The 5.5–11 millimeter long animals are arched, compact and short oval in shape. The coloring is mostly uniformly matt black, rarely only the elytra or the entire animal are colored black to reddish brown. Sometimes the pronotum has a faint metallic sheen or has a reddish-brown border at the base. The sensor flag is dark. The base of the pronotum is finely edged, its anterior angles are slightly drawn forward and the posterior angles are weakly edged. The flat spaces between the wing tops are finely and sparsely dotted, while the stripes in between are clear. The sides and the tip of the elytra have short hairs. The pygidium is edged, dull dark colored and finely dotted.
The head and pronotum show a clear sexual dimorphism in Onthophagus taurus . This mainly consists in the development of two transverse strips on the head shield , of which the front 'front strip' and the rear 'crown strip' are called.
The head of the male is strongly arched and slightly pointed. The forehead and crown are finely and sparsely dotted. The forehead ridge is usually missing or poorly developed. In large animals, the apex bar is drawn back into two long, slender, curved horns. However, these are often shortened, especially in the case of smaller specimens, or reduced to two blunt bumps at the end of a raised transverse bar. The pronotum falls obliquely forward in the male, has a longitudinal impression in the middle and is slightly bulged above it. The entire pronotum is only extremely fine, dotted even finer towards the base.
In the females, the forehead bar is clearly formed, the crest bar is only simply shaped. The former is slightly curved, the latter short and straight. The puncture of the head is denser and stronger compared to the males. The front fall of the pronotum is short and without bulge-like swellings. On the entire pronotum, the puncture is also stronger and denser than in the male.
The differentiation of Onthophagus taurus from the extremely similar species Onthophagus illyricus is difficult. In the latter, a bronze to greenish metal shimmer occurs much more frequently on the pronotum and elytra. The spaces between the wing covers are more dotted and the wing covers are also finely hairy on top. There are also differences in the structure of the male genitals. Both species also occur together in one habitat and together form the subgenus Onthophagus s. st. .
Occurrence
The species is common in southern and southern central Europe. It is also widespread in North Africa, the Middle East and Central Asia. It was accidentally introduced and established in North America in the late 1960s. It was also introduced in Australia.
Way of life
The larvae of Onthophagus taurus need dung, preferably from horses and cattle, to develop . The adults also feed on it. There can be more than 100 individuals in fresh dung heaps. The females dig gross tunnels under piles of manure and transport parts of the manure into the tunnels. Balls are formed from the manure and placed at the end of the tunnel. Then a small egg chamber is dug into the dung ball in which a single egg is placed. The egg chamber is closed and the egg is then left to its own devices. All of the larva’s food consists of the dung ball shaped for them.
Although the females take on most of the brood care , at least the horned males cooperate with them and help bring in the dung.
The horns on the pronotum of the males represent secondary sexual characteristics . They are used in aggressive fights for access to the females' breeding tunnels. The fights always take place inside the tunnels. The head and thorax are pressed down against the opponent, the abdomen is held up and the animals support themselves with their legs on the tunnel walls. In this way the animals can move up to 1141 times their own body weight. If an animal loses its grip, the stronger opponent either pushes it out of the tunnel or pushes it into the tunnel until it is wide enough that the stronger male can climb over his weaker competitor and then drive him out of the tunnel from below. The length of the horns is an indicator of success in fights - males with longer horns won significantly more often in fights. The winner is the owner of the gross tunnel and is allowed to mate with the female. Horned males usually stay with a female, guard her, and help complete the gross tunnel.
The males, who have only reduced horns or no horns at all, use a different strategy. They stay hidden at the entrance of the already occupied gross tunnel and sneak into the tunnels to meet the females when their partner is just outside the tunnel. Or they hide in the sometimes heavily branched gross tunnel system and thus avoid the dominant male. Due to the lack of horns, they move much more skillfully than their horned competitors. Mating can also take place outside the brood tunnel when the female is collecting manure for the brood. In this way, even smaller males can mate successfully. However, these males rarely help with brood care, but keep moving away from the breeding tunnel to find more mating partners.
Whether a male develops horns or not depends on the nutritional situation of the larva. Due to the two different reproductive strategies, it makes sense for the animals to develop either particularly large horns or none at all. Therefore, intermediate forms are extremely rare in the wild. From a certain critical height, horns are developed, including none.
Before mating, the male drums his forelegs on top and on the sides of the female's elytra. It only stops until the female moves into the mating position and copulation can begin. Copulation takes about one to two and a half minutes and is usually terminated by the female by stripping off the male.
Individual evidence
- ^ Theodor CH Cole: Dictionary of Invertebrates / Dictionary of Invertebrates: Latin-German-English . Springer-Verlag, 2016, ISBN 978-3-662-52869-3 ( google.de [accessed on February 17, 2019]).
- ↑ S. Schenkling: Explanation of the scientific beetle names from Reitter's Fauna Germanica. KG Lutz 'Verlag, Stuttgart 1917.
- ↑ a b c d e f Armin P. Moczek: Facultative paternal investment in the polyphenic beetle Onthophagus taurus: the role of male morphology and social context. In: Behavioral Ecology. 1999. Volume 10, Issue 6, pp. 641-647.
- ↑ a b c d e Armin P. Moczek, Douglas J. Emlen: Male horn dimorphism in the scarab beetle, Onthophagus taurus: do alternative reproductive tactics favor alternative phenotypes? In: Animal Behavior. 2000. No. 59, 459-466.
literature
- Vladimír Balthasar : Monograph of the Scarabaeidae and Aphodiidae of the Palaearctic and Oriental regions. Volume 2: Coprinae (Onitini, Oniticellini, Onthophagini). Publishing house of the Czechoslovak Academy of Sciences. Prague, 1963.
- Heinz joy , Karl-Wilhelm Harde , Gustav A. Lohse : The beetles of Central Europe. Volume 8: Teredilia, Heteromera, Lamellicornia. Goecke & Evers publishing house. Krefeld, 1969.
