Dynastes

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Hexapoda
Classis: Insecta
Cladus: Dicondylia
Subclassis: Pterygota
Cladus: Metapterygota
Infraclassis: Neoptera
Cladus: Eumetabola
Cladus: Endopterygota
Superordo: Coleopterida
Ordo: Coleoptera
Subordo: Polyphaga
Infraordo: Scarabaeiformia
Superfamilia: Scarabaeoidea

Familia: Scarabaeidae
Subfamilia: Dynastinae
Tribus: Dynastini
Genus: Dynastes
Species (7): D. grantii – D. hercules – D. hyllus – D. maya – D. neptunus – D. satanas – D. tityus
Name

Dynastes MacLeay, 1819: 22

Placed on the Official List of Generic Names in Zoology by ICZN (2014)
Type species: Scarabaeus hercules Linnaeus, 1758 by subsequent designation by Kirby (1825).

Synonyms

Theogenes Burmeister, 1847

References
Primary references

Macleay, W.S. 1819. Horae entomologicae: or essays on the annulose animals. Containing geneal observations on the geography, manners, and natural affinities of the Insects which compose the genus Scarabaeus of Linnaeus; to which are added a few incidental remarks on the genera Lucanus and Hister of the same author. With an appendix and plates. Vol. 1. Part 1. London: S. Bagster, xxx + [2] + 160 pp., 3 pls. BHL Reference page. [original description: p. 22]

Additional references

Iannacone-Oliver, J.; Soras-Vega, A. 2012: Dynastes (Macleay, 1819): distribución, lista de especies para Sudamérica y Crianza en Cautiverio. Scientia, 12(12): 81–103. PDF
Kirby, W. 1825: A description of such genera and species of insects, as alluded to in the "Introduction to Entomology" of Messrs. Kirby and Spence, as appear not to have been before sufficiently noticed or described. Transactions of the Linnean Society of London, 14: 563–572. Internet Archive
Ratcliffe, B. C., R. D. Cave, and E. Cano. 2013. The dynastine scarab beetles of Mexico, Guatemala, and Belize (Coleoptera: Scarabaeidae). Bulletin of the University of Nebraska State Museum 27: 1–666.

Links

Schoolmeesters, P. 2017. Scarabs: World Scarabaeidae Database (version Jul 2016). In: Roskov Y., Abucay L., Orrell T., Nicolson D., Bailly N., Kirk P., Bourgoin T., DeWalt R.E., Decock W., De Wever A., Nieukerken E. van, Zarucchi J., Penev L., eds. 2017. Species 2000 & ITIS Catalogue of Life, 30th January 2017. Digital resource at www.catalogueoflife.org/col. Species 2000: Naturalis, Leiden, the Netherlands. ISSN 2405-8858. Reference page. [accessed on Jun 10, 2017]

Dynastes is a genus of large beetles belonging to the family Scarabaeidae. They occur in the Nearctic realm and in the Neotropical realm, from the United States to Brazil;[1][2] four North American species (including Mexico), three with distributions extending from Central America either north or south, and two species endemic to South America.[2]

Description
Dynastes head and prothorax showing the pliers

Males of Dynastes bear two long horns, one on the head, and the other on the pronotum, forming a "plier"; the pronotal horn has reddish setae on its underside. This pronotal horn is absent in females.[3] Some species have an iridescent colouration to their elytra.[4] Certain species of the genus Dynastes also have the ability to change colour.[5] Specific species have been noted to occur with either black or yellowish to khaki green elytra.[5] This variation in colour is due to a spongy layer below the transparent cuticle;[5] this spongy layer is a network of filamentous strands made up of three-dimensional photonic crystals lying parallel to the cuticle surface.[6] When the cuticle is filled with gas this layer can show through, presenting the yellow to khaki green colour, but when filled with fluid the cuticle appears black.[5] This is due to the change in refraction index allowing us to see the difference in colours.[6] This system is known as a hygrochromic effect.[4] Female beetles can change colour but not as completely as males, which is not yet explained as the mechanisms for the colour change is still not completely understood.[5] What is known is that changes in humidity affect the levels of moisture in the cuticle which leads to a change in colour in most cases.[5] Since the change is due to humidity it is a reversible process, however, it has been observed that after multiple colour changes or high stress the beetles will maintain some dark spots on their cuticle.[4] Some hypotheses for why this colour change occurs at all are the ability to blend with surroundings depending on the time of day (black for nighttime and yellow for daytime) to best avoid their main predator, the tropical screech owl (Megascops choliba).[5] Another theory has to do with thermoregulation in the sense that a black beetle heats up faster than yellow and then once they have warmed up theoretically there will be less moisture in the cuticle which leads to changing to a colour which does not heat as quickly so they won't overheat.[5]
Species

There are eight species currently recognized in the genus, not counting putative subspecies of D. hercules:

Male	Female	Larvae	Scientific name	Common Name	Distribution
			Dynastes grantii Horn, 1870	Western Hercules beetle or Grants' Hercules beetle	USA: Arizona
			Dynastes hercules (Linnaeus, 1758)	Hercules beetle	Central and South America
			Dynastes hyllus Chevrolat, 1843		Mexico, Belize, El Salvador, Honduras, Guatemala, Nicaragua. Male: 35–70 mm (1.4–2.8 in); female: 30–45 mm (1.2–1.8 in)
			Dynastes moroni Nagai, 2005		Sierra de los Tuxtlas in Mexico
			Dynastes maya Hardy, 2003	Maya white beetle[7]	Mexico, Guatemala. Male: 50–90 mm (2.0–3.5 in); female: 40–50 mm (1.6–2.0 in)
			Dynastes neptunus (Quensel in Schönherr, 1805	Neptune beetle	South America: Colombia
			Dynastes satanas Moser, 1909	Satanas beetle	Bolivia. Male: 50–115 mm (2.0–4.5 in); female: 30–55 mm (1.2–2.2 in)
			Dynastes tityus (Linnaeus, 1763)	Unicorn beetle or Eastern Hercules beetle	United States[8]

Hybridization

Although there are numerous species under the genus Dynastes, some are able to produce viable offspring with one another.[2] This has been observed in captivity, but it is unclear if wild beetles will engage in acts of hybridization.[2] Certain species such as D. grantii and D. hyllus are believed to be sister species, while D. tityus is thought to be a sister taxon to the Central American "white Hercules" lineage.[2] The intermediate species that bridges the "white Hercules" and the "giant Hercules" lineages is thought to be D. maya.[2]
Life cycle

The larval stage of Dynastes hercules will last one to two years, with the larva growing up to 4.5 inches (11 cm) in length and weighing more than 100 g (3.5 oz). Much of the life of the larva is spent tunneling through rotting wood. After the larval period, transformation into a pupa, and moulting, the beetle then emerges as an adult. Adults of most species can live from two to ten months[9] and some can even live one or two years. Eastern Hercules beetles, D. tityus, can live six to twenty-three months in captivity with a hibernation period.[9] Western Hercules beetles, D. grantii, tend to have a shorter adult lifespan in the wild (two to four months), but in captivity they live for about the same amount of time as the eastern species.[9] It has also been noted that captive longevity is possible without a hibernation period.[9]

Bibliography

Hardy, 2003 - Description of a new species of Dynastes Kirby, Besoiro, Nr. 9
Lachaume (G.), 1985 - The Beetles of the World, volume 5, Dynastini 1. (Dynastidae) [2]

References

[1] Dynastes hercules at UFL
Huang, Jen-Pan (2016-10-15). "Parapatric genetic introgression and phenotypic assimilation: testing conditions for introgression between Hercules beetles (Dynastes, Dynastinae)". Molecular Ecology. Wiley. 25 (21): 5513–5526. doi:10.1111/mec.13849. hdl:2027.42/134423. ISSN 0962-1083.
Generic Guide to New World Scarab Beetles
Rassart, M; Colomer, J-F; Tabarrant, T; Vigneron, J P (2008-03-11). "Diffractive hygrochromic effect in the cuticle of the Hercules beetle Dynastes hercules". New Journal of Physics. IOP Publishing. 10 (3): 033014. doi:10.1088/1367-2630/10/3/033014. ISSN 1367-2630.
Hinton, H.E.; Jarman, G.M. (1973). "Physiological colour change in the elytra of the Hercules beetle, Dynastes hercules". Journal of Insect Physiology. Elsevier BV. 19 (3): 533–549. doi:10.1016/0022-1910(73)90064-4. ISSN 0022-1910.
Kim, Jae Hyun; Moon, Jun Hyuk; Lee, Seung-Yop; Park, Jungyul (2010-09-06). "Biologically inspired humidity sensor based on three-dimensional photonic crystals". Applied Physics Letters. AIP Publishing. 97 (10): 103701. doi:10.1063/1.3486115. ISSN 0003-6951.
Maya white beetle, Open Cage
Biolib
Krell, Frank-Thorsten; Krell, Victoria H. I. (2015). "Longevity of the Western Hercules beetle, Dynastes grantii Horn (Coleoptera: Scarabaeidae: Dynastinae)". The Coleopterists Bulletin. Coleopterists Society. 69 (4): 760–760. doi:10.1649/0010-065x-69.4.760. ISSN 0010-065X.