40 Interesting Facts About Hercules Beetles (Genus Dynastes)
Hercules beetles are large and impressive insects. They are known for the long horns of the male, which act as pincers, and their ability to change colour. The insects are named after Hercules, the hero of Ancient Greek and Roman mythology who was famous for his tremendous strength. The beetles are often attractive animals and have some interesting features and behaviour.
This article describes forty facts about the Hercules beetle of tropical parts of the world and the western and eastern Hercules beetles of the United States. The three insects belong to the genus Dynastes and the family Scarabaeidae. The members of the family are often called scarab beetles.
The Hercules beetle has the scientific name Dynastes hercules. The insect is found in Central and South America and the West Indies. It belongs to the family Scarabaeidae and the subfamily Dynastinae. The members of this subfamily are known as rhinoceros beetles.
External Anatomy of the Hercules Beetle
1. As in other insects, the body of a beetle is divided into three sections: the head, the thorax, and the abdomen. Also as in other insects, a beetle has three pairs of legs, which are attached to the thorax.
2. Beetles have two pairs of wings. Like the legs, they are attached to the thorax, but when they're folded they extend over the abdomen. The forewings are known as the elytra. They are hardened and serve to protect the delicate hindwings, which are hidden underneath and are used for flight. The elytra are moved out of the way when a beetle takes to the air.
3. The male Hercules beetle is black in colour, sometimes with the exception of the elytra. In a dry atmosphere, the elytra are yellow to olive green and are decorated with dark spots and fine streaks. When the atmosphere is humid, the elytra become completely black.
4. Females may be entirely black in a dry atmosphere but sometimes have elytra that are partially coloured. The colour possibilities are the same as those found in the males. As in the male, the colour fades in a humid environment. Females sometimes have a weaker ability to change colour than males, however.
5. The male has two extensions at the front of his head, which are known as horns. The length of the horns varies, but the upper one is generally much longer than the lower one.
6. Beetles have compound eyes and chewing mouth parts. The eyes of a Hercules beetle are located on the sides of the head below the lower horn (if it's present).
The cuticle is the outer covering of an insect's body. Researchers say that the colour of a dry Hercules beetle depends on the structure of the cuticle in the elytra. When the cuticle contains water, its structure changes in a vital way and its ability to create colour disappears.
Facts About the Horns
7. The upper horn of the beetle is called the thoracic horn, since it begins at the thorax, and the lower one the cephalic horn because it begins at the head. ("Cephalic" means of or relating to the head.)
8. Adults Hercules beetles are around two to three inches in length, not including the horn. The male may be as long as seven inches if his thoracic horn is included in the measurement. The insect is listed as the longest insect in the world with respect to total length by Guinness World Records. The titan beetle of South America has the longest body length, however.
9. The length of the horns depends on a variety of factors, including genetics, nutrition, and environment. The thoracic horn is usually considerably longer than the cephalic one.
10. The males use their horns for fighting with each other prior to mating with a female. The winner gains the right to mate.
11. The conflicts are sometimes only indirectly related to mating. The male maintains a territory during the mating season and fights to protect it from other males.
12. A male tries to grasp his adversary between his horns so that he can lift him into the air and then throw him to the ground. The fight continues until one of the beetles is injured, retreats, or is left upside down and helpless.
Habitat, Diet, and Behaviour
13. The Hercules beetle inhabits lowland and mountain rainforests.
14. The larvae live in wood from fallen trees. They feed on rotting wood and other decaying plant material.
15. The adult beetles are generally nocturnal or crepuscular (active at twilight). They can fly, but they usually stay on the ground, where they forage for food.
16. During the day, the adults hide in leaf litter. At night, they feed on fruits that have fallen to the ground.
17. The beetles are solitary animals except when a male and female meet to mate or when one male meets and confronts another one.
18. Observers say that the beetle creates a huffing sound by rapidly vibrating its abdomen against its elytra. This sound may act as a warning to predators.
19. The beetle exhibits complete metamorphosis. The developing insect goes through four stages, each of which looks different from the one before. The first stage is the egg. This is followed by the larvae, or grubs, and then the pupa. The pupa becomes an adult.
20. Many details of the beetle's reproduction have been discovered by observing captive animals. The insects are sometimes kept as pets. The reported time for each stage varies considerably and may depend on environmental conditions, such as temperature
21. The female lays up to a hundred eggs either in the ground or inside wood lying on the ground. She leaves the eggs unattended.
22. The eggs hatch in around twenty-eight to thirty days. Three larval stages, or instars, follow. The beetle remains in a larval stage for twelve to eighteen months.
23. The last larval stage eventually becomes a pupa. In this stage, the developing insect is covered by a hard case made of soil and its own feces.
24. After one to three months, an adult beetle emerges from the pupal case. The adult may live for three to twelve months longer. The reported time period is highly variable. The total lifespan of the insect is often said to be somewhere between two and three years.
The compound eye of the beetle above can be seen behind the lower horn. The appendage attached to the mouthparts is called a palp. The palps of a beetle help to manipulate food.
Eastern Hercules Beetles
25. The United States contains two species of Hercules beetles that are related to the tropical species. They share features with Dynastes hercules, but in some cases these features are slightly different from their form in the tropical beetle.
26. The scientific name of the eastern Hercules beetle is Dynastes tityus. It lives in the eastern part of the United States. Texas is the western limit of its distribution.
27. The beetle is two to three inches long including the male's horns. The horns are shorter than those of Dynastes hercules. The upper horn is referred to as the pronotal one and the lower one as the clypeal one. The pronotum is the plate covering the thorax. The clypeum is the lowest plate on the "face" of an insect.
28. The two horns are approximately the same size. The tip of the pronotal horn has a short bifurcation, which helps in identifying the species.
29. The male has a smaller horn on either side of his pronotal one, as shown in the photo above.
30. The pronutum and the elytra are yellow, tan, green, or grey and are mottled with black spots.
31. The surface of the beetle become entirely black in high humidity.
32. The beetles feed on fallen fruit. They have also been observed feeding on the sap from ash trees. They aren't considered to be a pest, however.
Because of their large size and impressive horns, many people believe that Hercules beetles are dangerous. In fact, their horns are not dangerous at all, and the beetles are not known to bite. However, if you pick one up, it may scratch you with its strong, spiny legs.— University of Kentucky
The American Hercules beetles reproduce by complete metamorphosis. This involves the same stages as the process in their tropical relative. The eggs, larvae, and pupa of the beetles develop in the soil.
The Western Hercules Beetle
33. The western Hercules beetle has the scientific name Dynastes grantii. The species name is sometimes written as granti, but according to entomologists this spelling is incorrect.
34. The beetle is found in Arizona, New Mexico, Utah, and northern Mexico.
35. Like its eastern relative, it's two to three inches in length.
36. Its pronotum and elytra are always grey-green in colour in a dry environment. The elytra are mottled with dark spots. The body becomes black in a humid environment.
37. The male's horns are noticeably longer than those of the eastern Hercules beetle. In addition, the pronatal horn is considerably longer than the clyneal one.
38. Unlike that of the eastern Hercules beetle, the pronatal horn doesn't have a bifurcation at the tip.
39. The insect feeds on the sap of ash trees.
40. Hybrids between the eastern and western Hercules beetles have been produced in the laboratory. Some researchers feel that the animals should be classified as members of the same species and that their differences are relatively minor geographical variations.
The two beetles shown in the video below have just come out of a humid box and are still dark in colour, particularly the female.
An Interesting Genus of Beetles
It's still uncertain why the different types of Hercules beetles change colour. Since the nights are typically more humid where the beetles live, the beetles change to a black colour at that time. One idea that has been proposed is that this darkening may be useful by providing camouflage. Another idea is that the black colour enables the beetles to absorb more heat during the cooler nights. Perhaps the change to a lighter colour is helpful during the brighter and often warmer day. Like some others characteristics of the animal, the ability to change colour is intriguing. Dynastes is an interesting genus of beetles.
- Hercules beetle information from the University of Florida
- A report about Dynastes hercules from the University of the West Indies
- Beetle records from Guinness World Records
- Information about Hercules beetles from the University of Kentucky
- Facts about the eastern Hercules beetle from Texas A&M AgriLife Extension
- Dynastes grantii entry from BugGuide
- Information about Dynastes grantii from the University of Nebraska-Lincoln
Questions & Answers
Are the Eastern and Western Hercules beetles rare? Are they only native to North & South America?
The Eastern and Western Hercules beetles are native to the United States. The western species is also found in northern Mexico. From what I've read, the eastern beetle is not considered to be rare, but it's not an abundant insect. The western beetle is said to be relatively common in Arizona, but not elsewhere in the United States.Helpful 1
What purpose does the hair on the horn of the Hercules beetle serve? Seems a bit odd but quite attractive.
I haven't found information about the function of the hairs on the horn of the Hercules beetle, but I have for the hairs of other members of its family (the Scarabaeidae). In the beetle's relatives, the hairs have a sensory function.
What was the biggest beetle ever recorded?
According to Guinness World Records, the longest beetle in the world is the titan beetle (Titanus giganteus) of South America. The body of this insect can be as long as six inches. The heaviest beetle is the larva of the Goliath beetle of Africa, which can weigh up to three-and-a-half ounces.
© 2018 Linda Crampton