''Dynastes'' is a genus of large beetles belonging to the family Scarabaeidae. They occur in the

Nearctic realm The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America t ...

and in the Neotropical realm, from the United States to Brazil;
''Dynastes hercules'' at UFL four North American species (including Mexico), three with distributions extending from Central America either north or south, and two species endemic to South America.

Description

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.Generic Guide to New World Scarab Beetles
/ref> Some species have an iridescent colouration to their elytra. Certain species of the genus ''Dynastes'' also have the ability to change colour. Specific species have been noted to occur with either black or yellowish to khaki green elytra. This variation in colour is due to a spongy layer below the transparent cuticle; this spongy layer is a network of filamentous strands made up of three-dimensional photonic crystals lying parallel to the cuticle surface. 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. This is due to the change in refraction index allowing us to see the difference in colours. This system is known as a hygrochromic effect. 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. 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. 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. 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 The tropical screech owl (''Megascops choliba'') is a small species of owl in the family Strigidae. It is found in Costa Rica, Panama, Trinidad, and every mainland South American country. Taxonomy and systematics The taxonomy of genus ''Megasco ...

(''Megascops choliba''). 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.

Species

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

Hybridization

Although there are numerous species under the genus ''Dynastes'', some are able to produce viable offspring with one another. This has been observed in captivity, but it is unclear if wild beetles will engage in acts of

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

. 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. The intermediate species that bridges the "white Hercules" and the "giant Hercules" lineages is thought to be ''D. maya''.

Life cycle

The larval stage of '' Dynastes hercules'' will last one to two years, with the larva growing up to in length and weighing more than . Much of the life of the larva is spent tunneling through rotting wood. After the larval period, transformation into a pupa, and

moulting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

, the beetle then emerges as an adult. Adults of most species can live from two to ten months 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 Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...

period. 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. It has also been noted that captive longevity is possible without a hibernation period.

Gallery

File: Scarabaeidae - Dynastes satanas.JPG, '' Dynastes satanas'' File:Dynastes tityus.JPG, '' Dynastes tityus'' File:Dynastes neptunus 001.jpg, ''

Dynastes neptunus ''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;Besoiro ''Besoiro'' is a French entomological scientific journal. It is published by Patrick Arnaud and was established in 1995. The name means beetle in Portuguese. The taxa described are included in the Zoological Record. Following the cessation of publ ...

, Nr. 9 * Lachaume (G.), 1985 -

The Beetles of the World ''The Beetles of the World'' is a series of books devoted to Coleopterology. Sciences Nat published the 24 first volumes; the following volumes and the supplements were published by Hillside Books, Canterbury. The first book authored by Jacques Ri ...

, volume 5, Dynastini 1. (Dynastidae

References

External links

* * {{Taxonbar, from=Q511827 Dynastinae Scarabaeidae genera Taxa named by William Kirby (entomologist)