Dynastinae

Dynastinae or rhinoceros beetles are a subfamily of the scarab beetle family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – include Hercules beetles, unicorn beetles or horn beetles. Over 1,500 species and 225 genera of rhinoceros beetles are known.^[2]

Dynastinae Temporal range: Eocene–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Suborder:	Polyphaga
Infraorder:	Scarabaeiformia
Family:	Scarabaeidae
Subfamily:	Dynastinae MacLeay, 1819
Tribes
See text[1]

Many rhinoceros beetles are well known for their unique shapes and large sizes. Some famous species are, for example, the Atlas beetle (Chalcosoma atlas), common rhinoceros beetle (Xylotrupes ulysses), elephant beetle (Megasoma elephas), European rhinoceros beetle (Oryctes nasicornis), Hercules beetle (Dynastes hercules), Japanese rhinoceros beetle or kabutomushi (Allomyrina dichotoma), ox beetle (Strategus aloeus) and the Eastern Hercules beetle (Dynastes tityus).

Description

European rhinoceros beetle

European rhinoceros beetle – three stages from larva to adult: larva (back), pupa (center), and imago (front)

The Dynastinae are among the largest of beetles, reaching more than 15 centimetres (6 inches) in length, but are completely harmless to humans because they cannot bite or sting. Some species have been anecdotally claimed to lift up to 850 times their own weight.^[3] An extinct Eocene Oryctoantiquus borealis was the largest fossil scarabeid, with a length of 5 centimetres (2.0 in).^[4] Some modern Oryctini grew up to 7 cm (3 in).^[4] Common names of the Dynastinae refer to the characteristic horns borne only by the males of most species in the group. Each has a horn on the head and another horn pointing forward from the center of the thorax. The horns are used in fighting other males during mating season, and for digging. The size of the horn is a good indicator of nutrition and physical health.^[5]

The body of an adult rhinoceros beetle is covered by a thick exoskeleton. A pair of thick wings lie atop another set of membranous wings underneath, allowing the rhinoceros beetle to fly, although not very efficiently owing to its large size. Their best protection from predators is their size and stature, also avoiding many due to being nocturnal. When the sun is out, they hide under logs or in vegetation to camouflage themselves from the few predators big enough to eat them. If rhinoceros beetles are disturbed, some can release very loud, hissing squeaks created by rubbing their abdomens against the ends of their wing covers.

Ecology

These beetles' larval stages can be several years long. The larvae feed on rotten wood and the adults feed on nectar, plant sap, and fruit. First, the larvae hatch from eggs and later develop into pupae before they reach adulthood.

Mating

Male Japanese rhinoceros beetles (Allomyrina dichotoma) fight to dominate sap sites. Males use their horns to pry rival males off the area, which also may give them the chance to mate with a female. In this and other species that defend mating sites, larger males with larger horns mate more frequently, as they win more contests. Small males often avoid larger males and exhibit alternative strategies to gain access to females.^[6][7]

As pests

Some species, such as the coconut rhinoceros beetle (Oryctes rhinoceros), can become major pests, e.g., in tree plantations.^[8] Usually though, beetle population densities are not as high as in some other pest insects, and they typically prefer food trees which are already sick or dying from some other cause. Some species' larvae, however, will attack healthy trees or even root vegetables, and when they occur in large numbers, can cause economically significant damage. The fungus Metarhizium majus is a proven biocontrol agent for beetle infestation in crops.

Uses

Rhinoceros beetles have become popular pets in parts of Asia,^[9] due to being relatively clean, easy to maintain, and safe to handle. Also in Asia, male beetles are used for gambling fights.^[10] Since males naturally have the tendency to fight each other for the attention of females, they are the ones used for battle. To get the two male beetles to lock in combat, a female beetle is used, or a small noisemaker duplicating the female's mating call.

Entomologist Séverin Tchibozo suggests the larvae contain much more protein (40%) than chicken (20%) and beef (approximately 18%), and they could become a protein source for a large human population.^[11]

Dr. MinJun Kim, leading a team of engineers in National Science Foundation-funded research, examined the function and aerodynamics of Allomyrina dichotoma with the help of researchers in Drexel University's Mechanical Engineering Department and in collaboration with Konkuk University in South Korea. Rhinoceros beetles could play a big part in the next generation of aircraft design.^[12]

Tribes with selected genera and species

Agaocephalini

Antodon goryi

Auth: Burmeister, 1847. all genera:

1. Aegopsis Burmeister, 1847
2. Agaocephala Lepeletier & Audinet-Serville, 1828
3. Antodon Brême, 1845
4. Brachysiderus Waterhouse, 1881
5. Colacus Ohaus, 1910
6. Democrates (beetle) Burmeister, 1847
7. Gnathogolofa Arrow, 1914
8. Horridocalia Endrödi, 1974
9. Lycomedes (beetle) Breme, 1844
10. Mitracephala Thomson, 1859
11. Spodistes Burmeister, 1847

Cyclocephalini

Cyclocephala borealis (Cyclocephalini)

Auth: Laporte, 1840. Selected genera:

• Ancognatha Erichson, 1847
• Cyclocephala Dejean, 1821 (masked chafers)
• Dyscinetus Harold, 1869 (rice beetles)

Dynastini

Eupatorus gracilicornis (Dynastini)

Auth: MacLeay, 1819. Selected genera:

• Allomyrina Arrow, 1911 (including Trypoxylus)
  • Allomyrina dichotoma – Japanese rhinoceros beetle
• Chalcosoma Hope, 1837
  • Chalcosoma atlas – Atlas beetle
  • Chalcosoma moellenkampi – Moellenkampi beetle
  • Chalcosoma caucasus – Caucasus beetle
• Dynastes MacLeay, 1819
  • Dynastes hercules – Hercules beetle
  • Dynastes neptunus – Neptune beetle
• Eupatorus Burmeister, 1847
  • Eupatorus gracilicornis – Five-horned rhinoceros beetle
  • Eupatorus siamensis – Siamese beetle
  • Eupatorus birmanicus – Rabbit beetle
• Megasoma Kirby, 1825
  • Megasoma mars - Mars beetle
  • Megasoma elephas - Elephant beetle
  • Megasoma actaeon - Actaeon beetle
• Xylotrupes Hope, 1837
  • Xylotrupes gideon – Siamese rhinoceros beetle
  • Xylotrupes ulysses

Hexodontini

Auth. Lacordaire, 1856; all genera from Madagascar:

1. Hemicyrthus Reiche, 1860
2. Hexodon Olivier, 1789
3. Hyboschema Péringuey, 1901

Oryctini

Trichogomphus mongol (Oryctini)

Auth: Mulsant, 1842. Selected genera:

• Enema Hope, 1837
• Megaceras Hope, 1837
  • Megaceras briansaltini
• Oryctes Hellwig, 1798
  • Oryctes nasicornis – European rhinoceros beetle
  • Oryctes rhinoceros – coconut rhinoceros beetle
• Strategus Kirby, 1828
  • Strategus aloeus – ox beetle
• Trichogomphus Burmeister, 1847
• Xyloryctes

Oryctoderini

Auth. Endrödi, 1966; all genera:

1. Chalcasthenes Arrow, 1937
2. Chalcocrates Heller, 1903
3. Coenoryctoderus Prell, 1933
4. Hatamus Sharp, 1877
5. Melanhyphus Fairmaire, 1881
6. Neohyphus Heller, 1896
7. Onychionyx Arrow, 1914
8. Oryctoderinus Endrödi, 1978
9. Oryctoderus Boisduval, 1835
10. Paroryctoderus Dechambre, 1994

Pentodontini

Pentodon idiota (Pentodontini)

Auth: Mulsant, 1842. Selected genera:

• Diloboderus Sturm, 1826 monotypic Diloboderus abderus
• Ligyrus Burmeister, 1847
• Pentodon Hope, 1837
• Pericoptus Burmeister, 1847
• Tomarus Erichson, 1847

Phileurini

Phileurus valgus (Phileurini)

Auth: Burmeister, 1847; selected genera:

• Cryptodus MacLeay, 1819
• Phileurus Latreille, 1807

Notes

1. Bouchard, P., Y. Bousquet, A. Davies, M. Alonso-Zarazaga, J. Lawrence, C. Lyal, A. Newton, et al. (2011). "Family-group names in Coleoptera (Insecta)". ZooKeys, vol. 88, 1-972.
2. Beutel, Rolf G.; Leschen, Richard A.B., eds. (2016-03-21). Coleoptera, Beetles, Volume 1, Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). De Gruyter. doi:10.1515/9783110373929. ISBN 978-3-11-037392-9.
3. Kram, Rodger (1 March 1996). "Inexpensive load carrying by rhinoceros beetles". Journal of Experimental Biology. 199 (3): 609–612. doi:10.1242/jeb.199.3.609. PMID 9318326.
4. Brett Ratcliffe, Dena M. Smith, Diane Marie Erwin. "Oryctoantiquus borealis, New Genus and Species from the Eocene of Oregon, U.S.A., the World's Oldest Fossil Dynastine and Largest Fossil Scarabaeid (Coleoptera: Scarabaeidae: Dynastinae)". 2009. The Coleopterists Bulletin 59(Mar 2005):127-135 DOI:10.1649/0010-065X(2005)059[0127:OBNGAS]2.0.CO;2
5. "Why horn size matters when picking a mate". New Scientist.
6. Buchalski, Benjamin; Gutierrez, Eric; Emlen, Douglas; Lavine, Laura; Swanson, Brook (15 October 2019). "Variation in an Extreme Weapon: Horn Performance Differences across Rhinoceros Beetle (Trypoxylus dichotomus) Populations". Insects. 10 (10): 346. doi:10.3390/insects10100346. PMC 6835817. PMID 31618906.
7. Goczał, Jakub; Rossa, Robert; Tofilski, Adam (17 April 2019). "Intersexual and intrasexual patterns of horn size and shape variation in the European rhinoceros beetle: quantifying the shape of weapons". Biological Journal of the Linnean Society. 127 (1): 34–43. doi:10.1093/biolinnean/blz026.
8. Featured Creatures: Coconut rhinoceros beetle
9. "WHO? KNEW" (May 6, 2005) Current Science Vol.90 No.16
10. "Rhinoceros beetle gambling in Thailand". Archived from the original on 2012-04-12. Retrieved 2006-11-03.
11. Global Steak - Demain nos enfants mangeront des criquets (2010 French documentary)
12. "Engineers Unlock Secrets of Beetle Flight" (news story). ScienceDaily. April 11, 2012. ScienceDaily (Apr. 10, 2012) — Rhinoceros beetles could play a big part....

Further reading

• Endrödi, S. (1985). The Dynastinae of the World. Series Entomologica. Vol. 28. Dr. W. Junk Publishers. ISBN 978-9061931386.
• Dechambre (R.-P.) & Lachaume (G.) The Beetles of the World, volume 27, The genus Oryctes (Dynastidae), Hillside Books, Canterbury

External links

• Family SCARABAEIDAE
• Subfamily Dynastinae