''Dynastes'' is a genus of large

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s belonging to the family

Scarabaeidae The family Scarabaeidae, as currently defined, consists of over 35,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change. Several groups formerly tre ...

. 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 The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropics, tropical Ecoregion#Terrestrial, terrestrial ecoregions of the Americas and the entire South American temperat ...

, from the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

;
''Dynastes hercules'' at UFL four North America, North American species (including

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

), three with distributions extending from

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

either north or south, and two species endemic to

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Description

Male Male (Planet symbols, symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or Egg cell, ovum, in the process of fertilisation. A male organism cannot sexual repro ...

s of ''Dynastes'' bear two long horns, one on the

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

, and the other on the

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

, forming a "plier"; the pronotal horn has reddish

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

e on its underside. This pronotal horn is absent in

female An organism's sex is female ( symbol: ♀) if it produces the ovum (egg cell), the type of gamete (sex cell) that fuses with the male gamete (sperm cell) during sexual reproduction. A female has larger gametes than a male. Females and ...

s.Generic Guide to New World Scarab Beetles
/ref> Some species have an iridescent colouration to their

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

. Certain species of the genus ''Dynastes'' also have the ability to change

colour Color (or colour in Commonwealth English; see spelling differences) is the visual perception based on the electromagnetic spectrum. Though color is not an inherent property of matter, color perception is related to an object's light absorp ...

. 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 A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

; this spongy layer is a network of filamentous strands made up of

three-dimensional In geometry, a three-dimensional space (3D space, 3-space or, rarely, tri-dimensional space) is a mathematical space in which three values (''coordinates'') are required to determine the position (geometry), position of a point (geometry), poi ...

photonic crystal A photonic crystal is an optical nanostructure in which the refractive index changes periodically. This affects the propagation of light in the same way that the structure of Crystal structure, natural crystals gives rise to X-ray crystallograp ...

s 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 In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

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 ''Dynastes'' can change colour but not as completely as males, which is not yet explained as the mechanism for the colour change is still not completely understood. What is known is that changes in

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

affect the levels of

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed or absorbed phase. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some comme ...

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 (''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 A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

currently recognized in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

, not counting putative subspecies of ''D. hercules (

Hercules beetle The Hercules beetle (''Dynastes hercules'') is a species of Dynastinae, rhinoceros beetle native to the rainforests of southern Mexico, Central America, South America, and the Lesser Antilles. It is the List of largest insects#Beetles (Coleopter ...

)'':

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. 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

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

l 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 A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

, and

moulting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...

, 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 reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is mos ...

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''

Bibliography

* Hardy, 2003 - Description of a new species of ''Dynastes'' Kirby, Besoiro, 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

* * {{Authority control Dynastinae Scarabaeidae genera Taxa named by William Kirby (entomologist)