Onthophagus illyricus

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Onthophagus illyricus
Onthophagus illyricus, ♂

Onthophagus illyricus , ♂

Systematics
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Family : Scarab beetle (Scarabaeidae)
Subfamily : Scarabaeinae
Genre : Onthophagus
Type : Onthophagus illyricus
Scientific name
Onthophagus illyricus
( Scopoli , 1763)

Onthophagus illyricus is a beetle from the family of scarab beetles , of the subfamily Scarabaeinae is expected. The genus Onthophagus comprises over two thousand species in 29 subgenera. In Europe, the genus is represented by six sub-genera. Onthophagus illyricus belongs to the subgenus Onthophagus , whose sister species Onthophagus taurus (bull's head dung beetle) can also be found in Europe.

Onthophagus illyricus was temporarily classified as a subspecies of Onthophagus taurus . Despite the great physical similarity, the genetic differences are great. Based on these differences, it is assumed that the species split up about three to four million years ago in the Pliocene and that overlapping areas of distribution were only settled after the split.

The males appear in two different forms. If the development conditions are so favorable that the larvae exceed a critical size, so-called 'large males' with two imposing horns develop. If the critical size is not exceeded, 'small males' develop with only rudimentary horns. Large and small males follow different reproductive strategies.

Notes on names and synonyms

The beetle was first described in 1763 by the Austrian Scopoli as Scarabaeus illyricus . The site at Fetschenbach (today Idrijca ) was at the time of the first description in Austria in the Duchy of Carniola , but belonged to the South Slavic language area, and the South Slavic languages ​​were then called Illyrian languages. A few years later, under Napoleon , the area belonged to the Illyrian Provinces for a short time , and later to the Kingdom of Illyria . This explains the species name illyricus , which Scopoli gave to the beetle. Today it was found in Slovenia near the town of Idrija .

The genus Scarabaeus was subdivided several times , in 1802 Latreille separated the genus Onthophagus from the genus Copris . He placed them between the genera Onitis and Aphodius . Latreille counted sixteen species of the genus Onthophagus and did not mention Onthophagus illyricus . The generic name is from Altgr. όνθος “ónthos” for “dung” and φάγος “phágos” for “eater” and refers to the food source of beetles and larvae.

Description of the beetle

The beetle, six to eleven millimeters long, is matt black or black-brown and can have a metallic sheen (for example in Fig. 2). The body is arched and without the head only one and a half times as long as it is wide.

Onthophagus illyricus male.jpg Onthophagus illyricus front2.jpg
Fig. 1: Side view ♂ Fig. 2: Front view ♂
Onthophagus illyricus wing case.jpg
Fig. 3: Hairiness of the elytra

The antennae are nine-segmented and end in a three-leaved, round club. The upper jaws are membranous except at the root. The jaws are four-limbed, thread-shaped, the end limb is slightly longer than the previous ones. The lip buttons are tripartite, the first two links are bristly rough, the end link is barely visible hidden in the tip of the second link. The head has two cross bars, a front and a crown bar. However, these are only clearly visible in the female. In large males, the forehead ridge is very weak, with two long, slender horns in place of the apex ridge. They are bent to the side and back so that they hug the pronotum when the head is raised. However, the males can also have a different appearance (alternative phenotype). Smaller males remain polled or have only rudimentary horns. In the male, the forehead is more strongly and more densely punctured , whereas in Onthophagus taurus the puncture is fine and extensive. The head shield is not edged at the front, but broadly rounded.

Recent studies show that the structure of the epipharynx is also different in the two species.

The sides of the pronotum are not clearly outlined in front of the base, but at most barely noticeable. The pronounced surface of the pronotum is only slightly weaker than the punctured disc, but this is only visible with favorable exposure and magnification (compare the surface of the fall in Fig. 2 with the middle of the pronotum in Fig. 1). In Onthophagus taurus, on the other hand, the difference in the puncture above and in front of the pronotum is clearly pronounced. The base of the pronotum is without dimples.

The label is not visible.

Hairiness and puncturing of the elytra also differ in Onthophagus illyricus and Onthophagus taurus , which can, however, be overlooked very easily. In Onthophagus illyricus the puncturing is coarser (granular) than in Onthophagus taurus . In addition, Onthophagus illyricus has more hair on the elytra than its sister species, even if the hair is not very dense and short. The first spaces between the stripes can even be bare, but the third and fourth space between the wing covers is never bare as in Onthophagus taurus (Fig. 3).

The legs are relatively short, the thighs slightly expanded in the middle. All tarsi are five-limbed and weak, especially the front tarsi are much weaker than the rails, but not absent. The front rails are four-toothed. The end tooth of the front rail protrudes not only to the side, but also to the front. Opposite it is a movable end spur on the inside. The middle and rear rails are not extended like a saber. They are widened towards the end. The middle rails have two spurs at the end, the rear rails only one. In the females of Onthophagus illyricus the anterior splints are somewhat slimmer than in the females of Onthophagus taurus .

The differences in the structure of the genitals are more pronounced than the differences in the external body features and presumably largely rule out hybridization.

biology

Both Onthophagus illyricus and Onthophagus taurus are warmth-loving and show the same basic behavior: They feed on the excrement of various herbivores and omnivores, mate on the droppings and take care of the same brood. Representatives of both species can be found on the same dung heap. However, the reproductive cycle of the two species is at least partially different. In Onthophagus illyricus , the beetles of the previous year appear in late spring, the eggs begin to lay in June, and the new generation appears in July and August. The maximum frequency is in summer. In Onthophagus taurus , the beetle appears earlier, begins reproduction immediately, and the new generation appears at the beginning of summer. The frequency distribution shows two peaks, one in spring and one in summer.

In Onthophagus acuminatus , the large males fight for the females, the small males try to mate with the females behind the back of the large males without being noticed. Both tactics are successful. Presumably this also applies to Onthophagus illyricus .

The beetles dig tunnels in the ground under the dung heap and blind tunnels that branch off from them. Feces from the dung heap are carried into the side passages. The larvae feed on the introduced manure. If the side chambers are filled with manure, they are covered with an egg and sealed. Three larval stages are passed through during development.

In a comparative study it was shown that almost 80% of the filled chambers of Onthophagus illyricus were less than seven centimeters deep, only 20% were deeper than seven centimeters, in each case less than 14 cm. In Onthophagus taurus from the same site, however, over half of the brood chambers were found deeper than 14 cm and only 6% of the brood balls were less than seven centimeters deep.

distribution

The beetle is common in almost all of Europe except in the north. It is absent in the British Isles and in Scandinavia it is only reported from Sweden. It does not occur in alpine areas either, but it penetrates higher altitudes than Onthophagus taurus . On the other hand, it is absent in the south on Cyprus and Crete , but Onthophagus taurus is found on the two islands . Since the two beetles can still be mixed in older collections, the data are not very reliable.

Outside of Europe, the distribution area extends to West and Central Asia ( Syria , Mesopotamia , Iran , Afghanistan ).

literature

Individual evidence

  1. ↑ a b Retrieved on March 23, 2018 from Fauna Europaea
  2. ↑ Retrieved on March 23, 2018 from Fauna Europaea
  3. ^ KE Lauterbach: On the knowledge of Onthophagus taurus Schreber and Onthophagus illyricus Scopoli . In Entomological Sheets for the Biology and Systematics of Beetles ISSN  0013-8835
  4. ↑ a b c Astrid Pizzo et al .: Genetic and morphological differentiation patterns between sister species: the case of Onthophagus taurus and Onthophagus illyricus (Coleoptera, Scatabaeidae) . In Biological Journal of the Linnean Society Vol. 89, Issue October 2, 2006, pages 197-211 [1]
  5. ^ Ioannis Antonius Scopoli: Entomologia carniolica exhibens Insecta Carnioliae indigena et distributa in ordines, genera, species, varietates methodo Linnaeana Vienna 1763 p. 11 No. 25
  6. ↑ Piere André Latreille: Histoire Naturelle des crustacées et insectes Volume 10 Paris in XII (1802) page 108
  7. ↑ Sigmund Schenkling: Explanation of the scientific beetle names (genus)
  8. ↑ a b Astrid Pizzo et al .: Epipharynx shape as a tool to reveal differentiation patterns between insect sister species: insights from Onthophagus taurus and Onthophagus illyricus (Coleoptera, Scatabaeidae) . In: Organisms Diversity & Evolution . Volume 93, 2009, pp. 189-200, doi : 10.1016 / j.ode.2009.01.003 . ( free full text )
  9. ↑ Onthophagus at coleo-net
  10. ↑ a b L. M. Macagno, Armin P. Moczek, Astrid Pizzo: Rapid Divergence of Nesting Depth and Digging Appendages among Tunneling Dung Beetle Populations and Species . In The American Naturalis Vol. 187, No 5. May 2016 page 189 - 200 [2]
  11. ^ J. Hunt, LW Simmons: Maternal and paternal effects on offspring phenotype in the Dung-Beetle Onthophagus taurus . In: evolution. 54, 2000, p. 936, doi : 10.1554 / 0014-3820% 282000% 29054% 5B0936% 3AMAPEOO% 5D2.3.CO% 3B2 .
  12. ↑ Polish page on Art

Web links

Commons : Onthophagus illyricus  - Collection of images, videos and audio files