Grant's Hercules Beetle

Pronunciation

How to pronounce Dynastes grantii: //dɪˈnæstiːz ˈɡrænti.aɪ//

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Summary

Dynastes grantii, also known as Grant's Hercules Beetle, is a large rhinoceros beetle characterized by its distinctive horn in males and greyish-white elytra. It is primarily found in highland forest habitats of southwestern U.S. and northern Mexico, feeding on tree cambium. The species faces conservation challenges due to habitat loss and pest threats.

Physical Characteristics

Males exhibit a characteristic horn and range from 50-85 mm in length. They have greyish-white elytra with irregular black spots. Females lack the horn and both sexes can vary in body size from 35-60 mm (1.4-2.4 in), with captive-reared individuals reaching up to 80 mm (3.1 in).

Identification Tips

Males are identifiable by their horn, while females are hornless; coloration can indicate whether they are D. grantii or the similar D. hyllus.

Habitat

Typically inhabits highland forest habitats at or above 1,600 m (5,200 ft) above sea level, often associated with Arizona Ash trees.

Distribution

Found in southwestern United States (southern Utah, Arizona, western New Mexico) and parts of northern Mexico.

Diet

Adults feed on the cambium of ash trees, stripping bark from small branches to access the sap.

Life Cycle

Undergoes a six-stage life cycle from egg to adult, approximately two years from egg to pupation, with a pupal duration of about 30 days. Adults emerge from pupae between August and October, living two to four months in the wild, and up to nine months in captivity.

Reproduction

Females oviposit over 100 eggs after mating.

Conservation Status

Considered a 'Species of Greatest Conservation Need' (SGCN) in New Mexico, at risk due to threats such as the Emerald Ash Borer (EAB).

Ecosystem Role

Plays a role in the decomposition of wood and the recycling of nutrients in forest ecosystems.

Evolution

Part of the White Hercules beetle lineage, closely related to other North American and Central American taxa. Evidence of possible hybrids between D. grantii and D. tityus due to morphological similarities.

Similar Taxa

• Dynastes hyllus
• Dynastes maya
• Dynastes moroni
• Dynastes tityus

Misconceptions

Often misspelled as 'granti'.

Tags

• beetles
• rhinoceros beetles
• Hercules beetle
• Dynastes grantii
• conservation
• New Mexico