Bug FAQGrant's Hercules Beetle
Dynastes grantii · Order: Coleoptera · Family: Scarabaeidae
Also called: Southwestern Hercules Beetle, Western Hercules Beetle
Source: Wikipedia
Adults range from about 3.5 cm to 6 cm long, with some captive beetles reaching 8 cm. They live in high-elevation forests above roughly 1,600 m and are native to the southwestern United States and northern Mexico. Males have a prominent thoracic horn and black-spotted white elytra, while females lack the horn.
Source: Wikipedia
How to recognize it
The wing covers are white to gray-white with irregular black spots. Males have a large horn on the thorax; females do not.
Source: Wikipedia
Size
Body length varies from 3.5 cm to 6 cm, and captive individuals can grow up to 8 cm.
Source: Wikipedia
Where it lives
They are typically found in highland forest habitats above about 1,600 m.
Source: Wikipedia
What it eats
Adults feed on the cambium of ash trees, stripping bark from small branches to drink the sap.
Source: Wikipedia
Life cycle
They go through six stages: egg, three larval instars, pupa, then adult. Development from egg to the emergence of the adult takes about two years.
Source: Wikipedia
When you see it
Adults leave their pupal chambers between August and October.
Source: Wikipedia
Where it comes from
The species occurs in Arizona, New Mexico, Utah, and parts of northern Mexico.
Source: Wikipedia
Lookalikes
They belong to the White Hercules beetle group and look very similar to Dynastes hyllus; geographic origin is needed to tell them apart.
Source: Wikipedia
Where it is found in the US
Recorded in 9 of 51 states and DC. Most records: Arizona, New Mexico, Utah, Kansas, Illinois, Kentucky, Texas, Arkansas.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
How large do Grant's Hercules beetles get?
They are usually between 3.5 cm and 6 cm long, with some captive beetles reaching up to 8 cm.
Source: Wikipedia
Where are Grant's Hercules beetles found?
They live in the southwestern United States, Arizona, New Mexico, Utah, and in northern Mexico.
Source: Wikipedia
When are adult beetles active?
Adults emerge from their pupal chambers from August through October.
Source: Wikipedia
How can I tell a male from a female?
Males have a prominent thoracic horn, while females lack this horn.
Source: Wikipedia
Same family (Scarabaeidae)
Japanese BeetlePopillia japonicaDamages trees, gardens or crops
Common Green June BeetleCotinis nitidaDamages trees, gardens or crops
Phyllophaga crinitaPhyllophaga crinitaDamages trees, gardens or crops
European Rose ChaferCetonia aurata
Mediterranean Spotted ChaferOxythyrea funestaDamages trees, gardens or crops
Oriental BeetleExomala orientalisDamages trees, gardens or cropsSources
- Wikipedia: https://en.wikipedia.org/wiki/Dynastes_grantii
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-24.