Kelly’s Field Notes

Common Name: Rhinoceros Beetle & Stag Beetle

Order: Coleoptera

Family: Scarabaeidae (Rhinoceros beetle), Lucanidae (Stag beetle)

Species of Note:

• The Hercules beetle (Dynastes hercules) - longest extant beetle species (males may reach 7 inches in length, including their horn), one of the largest flying insects weighing in at 34 grams (1.2 oz).

• The giraffe stag beetle (Prosopocoilus giraffa) - largest stag beetle species

• The giant stag beetle (Lucanus elaphus) - largest insect in the U.S. associated with dead wood

Description:

Rhinoceros Beetles - Rhinoceros beetles are found on every continent but Antartica. They are large, thick beetles and some adults (Hercules beetle) can lift 850 times their weight! Rhinoceros beetles are herbivores; as adults they feed on sap, fruit, and nectar and as larvae decaying plant matter. Rhinoceros beetles display some pretty significant sexual dimorphism! Males have those big horn-like protrusions to fight each other for the ladies (on y-shaped and one smaller horn on the top of their head). The size of the horn depends on the male’s nutritional intake - less nutrition will form a smaller horn. Rhinoceros beetles come in a variety of colors; black, grey, brown, green, yellow, etc.

Stag Beetles - Stag beetles are found in regions with higher temperatures and loose soil (oddly enough in the U.K., but not Ireland!). Like our friends the rhinoceros beetles, stag beetles are also sexually dimorphic. The males have large mandibles, some almost as long as the beetle’s entire body! They use these mandibles to wrestle each other in order to win females. Male have very heavy heads, 18% of their total mass is head! Their bite is very painful. Their heads are so heavy they incur an increase of 26% energy expenditure when flying. They also make it difficult to run, with males having a 40% more energy costly run than females without the headgear. Males are also prone to falling over on occasion because their headgear sets them off balance.

Life Cycle:

Both beetles begin life as eggs either laid underground (rhinoceros beetles) or in rotting wood (stag beetle). Both beetle eggs take about three to four weeks to hatch, sometimes faster depending on species (coconut rhinoceros beetles hatch between 8-12 days). Stag beetle larvae spend 6 years munching on rotted wood before becoming pupae. Rhinoceros beetle larvae have a shorter larval period at about 8 months, they also feed on rotting wood and leaves. Larvae are big boys and girls! Rhinoceros beetle larvae can get up to 4 inches in length (10 cm) and stag beetle larvae

Pupation is a long process for both beetles (depending on species), for stag beetles it’s about 6-8 months and for rhinos around 2 weeks. As we’ve discussed with other insects with long larval stages, once they make it to adulthood it’s a short life. Stag beetle adults live for 3-6 weeks and rhinos for 3-4 weeks. Rhinoceros beetle adults feed on leaves, sap, fruit, and nectar; some invasive species are seen as agricultural pests. Stag beetle adults eat very little other than rotting fruit or other plant matter.

Super Powers:

Rhinoceros Beetle -

• Super strength! Some adults can lift 850 times their weight!

• Flight - it’s wonky, but they can do it.

Stag Beetle -

• Super strength! Males have huge mandibles for wrestling.

• Flight - slow guys but decently fast ladies.

Rhinoceros and Stag Beetles in Culture:

• In Japan, rhinoceros beetles are seen as “strong, good-looking, and grand insects.” Japanese culture is generally very welcoming to insects.

• In Japanese rhinoceros beetles are called kabutomushi - helmet insect

• Rhinoceros beetles are popular pets in Japan! They are also frequently characters in advertising, Anime, and other media.

• In several Asian countries, people will put two male rhinoceros beetles on a log to fight and place bets on who will win.

• The Pokémon Heracross is based on the Japanese Rhinoceros Beetle.

• Hawaii is currently facing an invasion of coconut rhinoceros beetles (Oryctes rhinoceros), which came from southeast Asia in 2013. Researchers have deployed drones with insecticide to combat their destruction of Hawaii’s coconut trees.

• Rhinoceros beetles are a food source in some east Asian countries.

• In Greek mythology Cĕrambus (grandson of Poseidon) was turned into a stag beetle by nymphs after he changed some of them into Poplar trees.

• In parts of Europe in the Middle Ages stag beetles were seen as creatures of the Devil.

• The oldest depiction of a stag beetle as art dates back to 4000 BC.

• Aristophanes, of Greece, describes a game where children would tie a string to the leg of a stag beetle and let them fly around. The French word “cerf-volant” for kite is the same word for stag beetle.

• There is an illegal market for exotic stag beetles which is pushing some species towards extinction. There are over a dozen stag beetle species listed as threatened or endangered on the IUCN Red List.

Book Recommendations:

Evans, Arthur V. “Beetles of Eastern North America." Beetles of Eastern North America. Princeton University Press, 2014.

Documentary recommendations:

• BBC’s Life hosted by Sir David Attenborough has a great stag beetle scene!

References:

Beebe, William. "Notes on the Hercules Beetle, Dynastes hercules (Linn.), at Rancho Grande, Venezuela, with special reference to combat behavior." Zoologica 32 (1947): 109-116.

Crumley, Bruce. “Drones Lead Hawaii’s Coconut Rhinoceros Beetle Battle.” DroneDJ, 13 Aug. 2022, dronedj.com/2022/08/12/hawaii-drones-beetle.

Deal, Laura. “Eat the Beetles? Rural People Losing Their Taste for a Crucial Food Source.” CIFOR Forests News, 7 Sept. 2016, forestsnews.cifor.org/25259/augosoma-beetles-cameroon-forests-food-security-bushmeat?fnl=en

Dornberg, Mike. “Coconut Rhinoceros Beetle - Oryctes Rhinoceros.” University of Florida Featured Creatures, entnemdept.ufl.edu/creatures/orn/palms/Oryctes_rhinoceros.htm. Accessed 28 Aug. 2022.

“Evolution of Diverse and Bizarre Stag Beetle Weapons – Atlas of Science.” Atlas of Science, atlasofscience.org/evolution-of-diverse-and-bizarre-stag-beetle-weapons.

Hendry, Lisa. “Stag Beetles: Facts about the UK’s Largest Beetle and Where to See It.” The Natural History Museum, London, www.nhm.ac.uk/discover/stag-beetles.html.

Hoshina, Hideto, and Kenta Takada. "Cultural coleopterology in modern Japan: the rhinoceros beetle in Akihabara culture." American Entomologist 58.4 (2012): 202-207.

Farmer, Sarah. “Giant Stag Beetles.” CompassLive, 1 June 2017, www.srs.fs.usda.gov/compass/2017/06/01/giant-stag-beetles.

Williams, Rob. “Stag Beetle.” Texas A&M Extension Entomology, 14 Mar. 2018, extensionentomology.tamu.edu/insects/stag-beetle.

“Rhinoceros Beetles.” National Wildlife Federation, www.nwf.org/Educational-Resources/Wildlife-Guide/Invertebrates/Rhinoceros-Beetles.