The Hercules beetle (''Dynastes hercules'') is a species of
rhinoceros beetle
Dynastinae or rhinoceros beetles are a subfamily of the scarabaeidae, scarab beetle family (biology), family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – include Hercules beetles, unicorn be ...
native to the
rainforest
Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...
s of southern
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 ...
,
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 ...
,
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 ...
, and the
Lesser Antilles
The Lesser Antilles is a group of islands in the Caribbean Sea, forming part of the West Indies in Caribbean, Caribbean region of the Americas. They are distinguished from the larger islands of the Greater Antilles to the west. They form an arc w ...
''Dynastes hercules'' is known for its tremendous strength and is named after
Hercules
Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures.
The Romans adapted the Gr ...
, a hero of
classical mythology
Classical mythology, also known as Greco-Roman mythology or Greek and Roman mythology, is the collective body and study of myths from the ancient Greeks and ancient Romans. Mythology, along with philosophy and political thought, is one of the m ...
who is famed for his great strength.
Taxonomy
''D. hercules'' has a complex taxonomic history and has been known by several synonyms. It is in the subfamily
Dynastinae
Dynastinae or rhinoceros beetles are a subfamily of the scarabaeidae, scarab beetle family (biology), family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – include Hercules beetles, unicorn be ...
(rhinoceros beetles) in the larger 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 ...
(commonly known as scarab beetles). Not counting subspecies of ''D. hercules'', seven other species are 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 ...
sexually dimorphic
Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
, with only males exhibiting the characteristic horns (one on the head, and a much larger one on the pronotum). The body of males is black with the exception of the elytra, which can have shades of olive-green. They have a black suture with sparsely distributed black spots elsewhere on the elytra. They have a slightly iridescent coloration to their elytra, which varies in color between specimens and may be affected by the humidity of the local environment in which they develop.. At low humidity the elytra are olive-green or yellow in color, but darken to black at higher humidity due to its hygrochromic properties.
Females of ''D. hercules'' have punctured elytra which are usually entirely black, but sometimes have the last quarter of the elytra colored in the same way as the males.
File:Dynastes hercules (female).jpg, Female
File:Dynastes hercules hercules01.JPG, Male
File:" Hercules beetle illustration from The Naturalist's Miscellany (1789-1813) by George Shaw (1751-1813). ".jpg, Hercules beetle illustration from ''The Naturalist's Miscellany'' (1789–1813) by George Shaw (1751–1813).
Distribution and habitat
Populations of ''D. hercules'' may be found from southern Mexico to Bolivia in mountainous and lowland rain forests. Known populations include the Lesser Antilles, Trinidad and Tobago, Brazil, Ecuador, Colombia, and Peru.Chromosomal analysis has shown that the genus ''Dynastes'' originated from South America.
Life cycle
Not much is known about the life cycle in the wild, but much evidence has been gained through observations of captive-bred populations. The mating season for adults typically occurs during the
rainy season
The rainy season is the time of year when most of a region's average annual rainfall occurs.
Rainy Season may also refer to:
* ''Rainy Season'' (short story), a 1989 short horror story by Stephen King
* "Rainy Season", a 2018 song by Monni
* '' ...
(July to December). Females have an average gestation period of 30 days from copulation to egg-laying, and may lay up to 100 eggs on the ground or on dead wood. The eggs have an incubation period of approximately 27.7 days before they hatch. Once hatched, 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 the Hercules beetle may last up to two years in duration, where it will go through 3 metamorphosis stages, also known as
instar
An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
s. The larvae have a yellow body with a black head. The larvae can grow up to in length and weigh more than 100 grams. In laboratory conditions at 25 ± 1° C, the first instar stage lasts an average of 50 days, the second stage an average of 56 days, and the third an average of 450 days. After the third instar stage, the
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 ...
l stage lasts about 32 days, where it will transition into an adult. Adult beetles can live for three to six months in captivity.
Diet and behavior
Diet
The larvae of the Hercules beetle are saproxylophagous, meaning that they feed on rotting wood; they reside in same during their two-year developmental stage. The adult Hercules beetle feeds on fresh and rotting fruit, along with tree sap. Adults carve bark through the use of its synchronous mandibles to easily access the sap of trees. When these mandibles are closed, a narrow opening is formed which can act like a straw to allow consumption of tree sap. They have been observed feeding on peaches, pears, apples, grapes, bananas, and mangoes in captivity.Krell, F., Krell, V. Longevity of the Western Hercules beetle, ''D. grantii'' Horn (Coleoptera: Scarabaeidae: Dynastinae). ''The Coleopterists Bulletin'', vol. 69, 2015, 1p.
Behavior
Within their native rain forest habitats, the adult beetles, which are nocturnal, forage for fruit at night and hide or burrow within the
leaf litter
Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...
during the day. The adult ''D. hercules'' beetles are capable of creating a 'huffing' sound, generated by stridulating their abdomen against their elytra to serve as a warning to predators. Like most insects, communication within the species is a mix of chemoreception, sight, and mechanical perception. Experiments on ''D. hercules'' have shown that a male placed in the vicinity of a female will immediately orient towards her and seek her out, suggesting chemical communication through strong sexual pheromones.
Combat behavior between males
It has been observed in wild habitat and in captivity that male ''D. hercules'' will engage in combat to win possession and mating rights to a female. Male Hercules beetles typically use their large horns to settle mating disputes; these fights can cause significant physical damage to the combatants but may also include possible damage to the female in the process. During fights, the males attempt to grab and pin their rival between the cephalic and thoracic horns to lift and throw them. The successful male wins mating rights with the female, though the beetles remain
polygynandrous
Polygynandry is a mating system in which both males and females have multiple mating partners during a breeding season. In sexually reproducing diploid animals, different mating strategies are employed by males and females, because the cost of gam ...
.
Physical strength
Reports suggest the Hercules beetle is able to carry up to 850 times its body mass. Actual measurements on a much smaller (and relatively stronger: see square-cube law) species of rhinoceros beetle show a carrying capacity only up to 100 times their body mass, at which point they can barely move.
Relationship to humans
''Dynastes hercules'' does not negatively affect human activities, either as an agricultural pest or disease vector. The beetles can be kept as pets. Larvae excrement has been shown to contain β-mannanase, a bacterially synthesized enzyme that
hydrolyzes
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
hemicellulose
A hemicellulose (also known as polyose) is one of a number of heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all embryophyte, terrestrial plant cell walls. Cellulose is crystalline, strong, an ...
that can be used in enzyme based cleaning products. β-mannanase has been successfully extracted and cloned from larvae fecal matter, suggesting that production of bio additive cleaning products may be feasible.
Relationship to the environment
''Dynastes hercules'' is a beneficial contributor to the rain forest
ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
, primarily during their larval stage where they are saproxylophagous. Feeding on rotting wood assists with
biodegradation
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegrada ...