Larva Face

Kelly’s Field Notes

Common Name: Ironclad Beetles

Order: Coleoptera

Family: Zopheridae

Subfamily: Zopherinae

Genus: Phellopsis, Nosoderma, Zopherus

Species: There are around 31 described species of ironclad beetles.

• Diabolical ironclad beetle (Phloeodes diabolicus) - found only in the California floristic province and Baja, California.

• Reflexed Ironclad Beetle (Pycnomerus reflexus) - found throughout the eastern United States.

• Southwestern ironclad beetle (Zopherus nodulosus) - found throughout Texas and Mexico.

• Tim Tam beetle (Zopherosis georgii) - found in eastern Australia and named after the popular cookie/biscuit.

Description: 

Adult ironclad beetles are typically small to medium-sized, between 1.3 and 3.2 cm (0.5 to 1.25 in). They have a compact, heavily armored appearance. Their bodies are usually elongated, flat, and low to the ground (Machemer, 2020). Their exoskeleton is very thick and often contains ridges, tubercles, or deep punctures, giving them a rough, rugged texture. Ironclad beetle coloration tends to be dark (deep brown to black). Their head is often partially retracted into the pronotum (the shield-like covering over the front of the thorax), and the antennae are relatively short, usually ending in a club or gradual thickening toward the end.

The pronotum is wide and sometimes features margins that are serrated or uneven. The elytra are fused around the abdomen, locking in place, forming a rigid protective shell that reduces flexibility but increases defense against predators. This fusing has left ironclad beetles fairly uncrushable but also flightless.

Life Cycle:

Ironclad beetles undergo complete metamorphosis (egg, larva, pupa, and adult). Females typically lay their eggs in protected small spaces such as crevices in decaying wood or beneath bark, where the developing larvae will have immediate access to food. After hatching, the larvae are grub-like and feed primarily on decomposing wood and associated fungi, gradually growing before entering a pupal stage within the same environment. Adults feed on various fungi species. There is not a lot known about ironclad beetle biology in general (Texas A&M AgriLife Extension Service, 2017). Adults can live up to 8 years (Machemer, 2020)!

Nearly Uncrushable:

In 2015 Dr. Jesus Rivera found a diabolical ironclad beetle  (P. diabolicus) and did what anyone would do in his shoes. Drive over it with his Toyota Camry. Not once, but twice. His Toyota Camry weighs about 1,587 kgs (3,500 lbs). While the ironclad beetle pretended to be dead, it was fine. This little beetle can withstand the crushing force of 39,000 times its body weight. That is equivalent to a 68 kg (150 lb) person resisting the crushing force of 25 blue whales (Wu, 2020). Using an X-ray imaging technique at Berkeley Lab’s Advanced Light Source (ALS) synchrotron, and other techniques, Dr. Rivera and the other researchers on his team discovered the armor of the ironclad beetle was crushproof due to its structure. The elongated elytra wrap around the beetle, connecting underneath the abdomen, which forms a protective shell around the beetle. The joining of these pieces allows for some flex which distributes the weight of whatever is on the beetle evenly. Within that shell is a cushion of air which protects the beetle’s body from compression (Rivera et al., 2020).

Here is a video of those scans from Dr. Rivera’s lab: https://www.youtube.com/watch?v=EseTLvWTQiw

Ironclad beetles are so tough a drill is needed to pin one for your insect collection (Wallheimer, 2021)! Researchers are currently studying the beetles to develop stronger materials to use in aircraft and general construction (Machemer, 2020).

Beetles as Jewelry:

Ironclad beetles in the genus Zopherus (typically Zopherus chilensis) have a unique and somewhat controversial role as living jewelry in parts of Mexico. These beetles are used to create ornaments known as maquech or ma’kech, where live insects are decorated with rhinestones, beads, and small chains, then worn like brooches on clothing. 

This practice dates back to a Yucatán legend about a princess who is dating a man her father does not approve of. The lovers are discovered and the man is sentenced to death. But before he is killed a wise man or sorcerer turns him into a beetle that could be decorated and worn over the princess's heart as a reminder of their eternal bond (Jaggard, 2015). 

In Mexico, groups of men called "Los Maquecheros" find and collect adult ironclad beetles in the wild. They are then sold to vendors who decorate them and then sell them to tourists for around $5 to $10. This practice is regulated on a community basis but there are no laws dictating collection standards. While there are ethical issues with using live beetles as adornments there is also the issue of unknown damage to the beetle populations due to overharvest. Researchers have begun breeding them to take some of the pressure off of wild populations (Jaggard, 2015).

Super Powers:

• Uncrushable - ironclad beetles can withstand the crushing force of 39,000 times its body weight. Part of this need to go all in on being uncrushable is their long life. The longer an animal lives the more time it needs to put into survival. As Max Barclay says, the curator of beetles at the Natural History Museum in London, “These beetles are doing the beetle-equivalent of living for 1,000 years” (Machemer, 2020).

• Play Dead - when an ironclad beetle feels threatened it will often play dead.

• Long Lived - ironclad beetle adults can live for up to 8 years.

• Water Retention - the tightly sealed exoskeleton of an ironclad beetle prevents moisture loss, which is important to this arid group of beetles!

• Fashionable - these beautiful beetles are bedazzled and worn as living jewelry in Mexico.

References:

““Ironclad” Beetle - Field Guide to Common Texas Insects.” Field Guide to Common Texas Insects, Texas A&M AgriLife Extension Service, 10 July 2017, texasinsects.tamu.edu/coleoptera/ironclad-beetle/.

Jaggard, Victoria. “Meet the Makech, the Bedazzled Beetles Worn as Living Jewelry.” Smithsonian Magazine, 2015, www.smithsonianmag.com/smithsonian-institution/meet-makech-bedazzled-beetles-worn-living-jewelry-180955081.

Machemer, Theresa. “The Secrets of the Diabolical Ironclad Beetle’s Almost Unsquishable Strength.” Smithsonian Magazine, 22 Aug. 2020, www.smithsonianmag.com/smart-news/scientists-unravel-secrets-diabolical-ironclad-beetles-near-unsquishable-strength-180976113/. Accessed 27 Mar. 2026.

‌‌‌Rivera, Jesus, et al. "Toughening mechanisms of the elytra of the diabolical ironclad beetle." Nature 586.7830 (2020): 543-548.

Wallheimer, Brian. “Ironclad beetles offer a lot to learn for engineers and entomologists.” Purdue University, 15 Mar. 2021, ag.purdue.edu/news/2021/03/ironclad-beetles-offer-a-lot-to-learn-for-engineers-and-entomologists.html. Accessed 27 Mar. 2026.

‌Wu, Katherine J. “Meet the Diabolical Ironclad Beetle. It’s Almost Uncrushable.” The New York Times, 21 Oct. 2020, www.nytimes.com/2020/10/21/science/beetle-uncrushable-ironclad.html.