Hercules beetle

The Hercules beetle (Dynastes hercules) is a species of rhinoceros beetle native to the tropical forests of southern Mexico, Central America, South America, and the Lesser Antilles. It is the longest extant species of beetle in the world, and is also one of the largest flying insects in the world.

Etymology

Dynastes hercules is known for its tremendous strength and is named after Hercules, a hero of classical mythology 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 (rhinoceros beetles) in the larger family Scarabaeidae (commonly known as scarab beetles). Not counting subspecies of D. hercules, seven other species are recognized in the genus Dynastes.

Subspecies

Several subspecies of D. hercules have been named, though still some uncertainty exists as to the validity of the named taxa.

Dynastes hercules ecuatorianus Ohaus, 1913
Dynastes hercules hercules (Linnaeus, 1758)
Dynastes hercules lichyi Lachaume, 1985
Dynastes hercules morishimai Nagai, 2002
Dynastes hercules occidentalis Lachaume, 1985
Dynastes hercules paschoali Grossi & Arnaud, 1993
Dynastes hercules reidi Chalumeau, 1977 (= baudrii Pinchon, 1976)
Dynastes hercules septentrionalis Lachaume, 1985 (= tuxtlaensis Moron, 1993)
Dynastes hercules takakuwai Nagai, 2002
Dynastes hercules trinidadensis Chalumeau & Reid, 1995 (= bleuzeni Silvestre and Dechambre, 1995)

Description

Adult body sizes (not including the thoracic horn) vary between in length and in width. Male Hercules beetles may reach up to in length (including the horn), making them the longest species of beetle in the world, if jaws and/or horns are included in the measurement. The size of the horn is naturally variable, more so than any variation of the size of legs, wings, or overall body size in the species. This variability results from developmental mechanisms that coincide with genetic predisposition in relation to nutrition, stress, exposure to parasites, and/or physiological conditions.

Dynastes hercules is highly sexually dimorphic, 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. 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.

Life cycle

thumb|right|upright|The Larva of D. hercules is among the largest in any insect.

Not much is known about the life cycle in the wild, but much evidence has been gained through observations of captive-bred populations. Adults carve bark through the use of their 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.

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 during the day. 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. 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.

Relationship to humans

thumb|A human with a Hercules beetle

Dynastes hercules does not negatively affect human activities, either as an agricultural pest or disease vector. The beetles can be kept as pets.

Relationship to the environment

Dynastes hercules is a beneficial contributor to the forest ecosystem, primarily during their larval stage where they are saproxylophagous. Feeding on rotting wood assists with biodegradation and cycling nutrients in the environment.