Dynastes hercules

Geographic Range

Hercules beetles, Dynastes hercules , occur in the new world tropics of Central and South America. The southern Mexican border to west central Bolivia represent the species' northern and southern limitations, respectively. Within these boundaries Hercules beetles have been found in pockets of both montane and lowland rainforests from the Pacific Ocean as far east as the Brazilian Amazon. This includes all of Central America, the Pacific coast and Amazonia of Colombia, western Venezuela, the islands of Guadeloupe and Dominica, eastern Ecuador, central Peru, western Brazil, and west/central Bolivia. It is important to note that due to the inaccessibility of the Amazon rainforest and relative lack of research, this distribution remains only an approximation.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Hercules beetles inhabit the understory of montane and tropical rainforests. The larva of D. hercules , like many of its beetle relatives, takes up residence in decaying wood. Due to the sheer size of the larva, which can grow to longer than 15 cm and weigh up to 140 grams, the forest must provide fallen trees of adequate girth. Although the adult beetle is capable of flight it has been observed primarily in the undergrowth and the forest floor, inhabiting those areas which permanently retain moisture and provide a healthy supply of fallen fruit for consumption.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

Physical Description

Hercules beetles are some of the largest beetles and indeed, some of the largest insects alive today. The larva of D. hercules in its later instars (larval growth stages) can weigh up to 140 grams and barely fits in the outstretched hand of a male adult human. Upon pupating and emerging as adults the beetles actually lose some of their larval mass but still retain an imposing size. The most obvious and striking features of the adult male are the long horns that arise from the thorax (thoracic) and head (cephalic). Together, these appendages mimic both the appearance and function of a large claw. When measured from the end of the longer, thoracic horn to the tip of the abdomen, adult males average around 78 mm in length, though there are reports of massive males on the island of Guadeloupe reaching 180 mm long. Females lack horns and are smaller, averaging 61.8 mm long. The rest of the beetle’s physical characteristics are typical, albeit larger, for the family Scarabaeidae . Beneath the cephalic horn reside large eyes and distinct lamellate antennae (a straight stalk with right angled fingers at the terminus). The elytra (hardened front wings which create a shell around the abdomen) of D. hercules are noteworthy in that they change color with varying humidity levels. In low humidity, the elytra appear yellow to olive green but they turn stark black with rising moisture levels. The mechanism responsible for this change is the intricate microstructure of the elytra that modifies light refraction as it is exposed to moisture.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently
• ornamentation ornamentation

Development

Like all beetles, D. hercules goes through complete metamorphosis with egg, larval, pupal, and adult stages. Once the egg is laid, it develops for 1 month before hatching into a larva. The larval stage can last from 12 to 18 months before the 2 to 3 month pupal stage. Sexual maturity occurs upon emergence of the adult, or imago beetle.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Reproduction is sexual with a high degree of male competion. In controlled settings D. hercules females initiate sexual contact chemically, by the use of pheromones. Once receptiveness is communicated males will readily seek out the female. Males vying for copulatory rights to a single female will engage in complex battles using their horned weaponry. They attempt to clasp and subdue their opponent between the appendages. When one male is successful in this endeavor he lifts his opponent up as far as his segmented body will allow and slams his unfortunate victim down. This melee can go back and forth through multiple body slams before one male inevitably retreats. It is important to point out that these battles have all been observed in artificial conditions. It is possible wild males are competing on unstable or arboreal substrates and that the true purpose of these altercations is to grasp and throw the opponent off of the staging ground, thus eliminating the losers chances of reproductive success.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

There has been little research into the reproductive cycle of Hercules beetles. The few studies that have observed mating D. hercules have noted no seasonality with respect to the willingness to mate.

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Hercules beetles have never been observed to provide any type of parental care beyond egg laying. It is likely, as with other beetles, the eggs are laid directly into the decaying wood of a fallen tree where the larvae will live upon hatching, and then abandoned. Females likely do provide provisioning in the eggs though.

• Parental Investment
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

All information on Hercules beetle lifespan has been collected under artificial conditions. These data nonetheless give a general idea of the longevity of the species. The egg incubates for around one month before hatching into a larva. The larval stage can last from 12 to 18 months before the 2 to 3 month pupal stage. Once emerged, the adult beetle can live for 8 to 12 months making the potential lifespan 34 months.

Behavior

Field research on wild populations of D. hercules is sparse and most behavioral data pertains to captive experiments. One of the more peculiar behaviors of Hercules beetles is their ability to create a “huffing” sound by stridulating (rapidly vibrating) their abdomen against their elytra. It is thought this sound is used in predator defense, perhaps as a warning. As illustrated above, the horns of male beetles are important in sexual reproduction but may also be important for defense. The force exerted by the muscle that controls the thoracic horn has been measured at 140 Newtons (14.3 kg). Predation on D. hercules is undocumented, which may be a result of formidable armament mixed with sheer mass. Adding to this theory, D. hercules is generally cumbersome in both flight and on the ground, implying a more complex defensive strategy than simple evasion.

• Key Behaviors
• flies
• motile motile

Communication and Perception

Like most insects, communication within the species is a mix of chemoreception (the sensing of chemicals with specialized pores or appendages), sight, and mechanical perception. Dynastes hercules is also likely able to detect vibrations. Experiments have shown that a male placed in the vicinity of a female will immediately orient towards her and seek her out. This is evidence of communication through strong sexual pheromones. The huffing or hissing sounds produced when disturbed serve to communicate a warning to potential predators.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Hercules beetles are herbivorous with the larvae feeding on rotting wood and the adults foraging for fallen, rotting fruits among the undergrowth. In controlled settings they have been observed devouring bananas and mangos. They first pierce the skin of the fruit with their mouth parts then proceed to masticate the surrounding tissue into a soft, easy to process pulp. Given the opportunity, D. hercules will feed uninterrupted for up to 24 hours in artificial conditions.

• Primary Diet
• herbivore herbivore
  • frugivore frugivore
  • lignivore

• Plant Foods
• wood, bark, or stems
• fruit

Predation

No predation events on D. hercules have been observed and documented. Predators, especially on the succulent larvae, may include birds, bats, and small mammals such as rats.

Ecosystem Roles

Though no official studies of the ecological role of D. hercules have been conducted, based on the diet of decaying matter in both larval and adult forms, Hercules beetles aid in biodegradation and cycling of nutrients.

• Ecosystem Impact
• biodegradation biodegradation

Economic Importance for Humans: Positive

Hercules beetles are in high demand within the beetle enthusiast trade, which is especially prevalent in Japan. Large specimens of certain subspecies of D. hercules can sell for as much a $700 dollars.

• Positive Impacts
• pet trade pet trade
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of Dynastes hercules on humans.

Conservation Status

Dynastes hercules has no special conservation status. Because of the nature of its habitat little is known about the population density and fluctuations of D. hercules , though threats to its rainforest ecosystem include deforestation and climate change.

Additional Links

Encyclopedia of Life

Contributors

Andy Kulikowski (author), University of Wyoming, Hayley Lanier (editor), University of Wyoming - Casper, Angela Miner (editor), Animal Diversity Web Staff.

References

Beebe, W. 1944. Notes on the Hercules Beetle, Dynastes hercules (Linn.), a Rancho Grande, Venezuela, with special reference to combat behavior.. Zoologica: New York Zoological Society , 29/8: 53-58.

Blum, M. 1979. Sexual Selection and Reproductive Competition in Insects . Waltham, MA: Academic Press, Inc.

Campbell, C. 2012. " Dynastes hercules " (On-line). naturalworlds.org. Accessed November 11, 2013 at http://www.naturalworlds.org/scarabaeidae/species/Dynastes_hercules.htm .

Dutrillaux, B., A. Dutrillaux. 2013. A South American origin of the genus Dynastes ( Coleoptera : Scarabaeidae : Dynastinae ) demonstrated by chromosomal analyses. Cytogenetic and Genome Research , 141/1: 37-42.

Hinton, H., G. Jarman. 1973. Physiological colour change in the elytra of the Hercules beetle, Dynastes hercules . Journal of Insect Physiology , 19: 533-549.

Jarman, J., H. Hinton. 1974. Some defence mechanisms of Hercules beetle, Dynastes hercules . Journal of Entomology Series A-Physiology & Behavior , 49/NOV7: 71-80.

Kasahara, . 2006. "The Breeding/Rearing of Dynastes hercules hercules " (On-line). Accessed November 07, 2013 at http://www.naturalworlds.org/scarabaeidae/manual/hercules/Dynastes_hercules_breeding_1.htm .

Rassart, M., J. Colomer, T. Tabarrant, J. Vigneron. 2008. Diffractive hygrochromic effect in the cuticle of the Hercules beetle Dynastes hercules . New Journal of Physics , 10/3: 1-14.

2013. "Insect Price List/ Dynastidae " (On-line). Insect-Sale. com. Accessed November 14, 2013 at http://www.insect-sale.com/shop/store.asp?Item=Dynastidae&Code=Dy45 .

2013. "Rhinoceros Beetles" (On-line). Accessed November 07, 2013 at http://www.nwf.org/wildlife/wildlife-library/invertebrates/rhinoceros-beetles.aspx .

2013. "Threats:Deforestation" (On-line). WWF. Accessed November 14, 2013 at http://worldwildlife.org/threats/deforestation .