Back in May, during a bout of spring gardening, I wrapped my hands around the end of a rotting stump protruding from the dirt in my backyard and tugged. With a yank, it gave way, opening up a football-sized hole in the ground and exposing a glistening, translucent orb the sickly, pale color of a frostbitten finger. Eww.
I hollered for reinforcements and grabbed a stick to poke at the thing, which uncoiled slightly into what appeared to be the mother of all grubs. My neighbor picked it up in his gloved hand, and after his kids admired it a while and I took a video, we dropped it back in the ground and covered it up, in hopes that in a few months some fantastical creature might emerge.
A few months later, a similar thing happened to an acquaintance. “My dad was digging up some remains of an old stump so the grass could grow back in, when what turned up but that big juicy fellow,” said Matt Wise, a freelance mediator and gardener in Austin, when I asked him about the monster grub whose photo he’d posted on social media. Were we under invasion? And if so, by what?
I contacted entomologist Ed Riley, the former associate curator of the Texas A&M University Insect Collection, who told me that the jumbo-sized larvae Wise and I had seen were likely one of two species of rhinoceros beetle that live in Central Texas. (Our state is also home to two slightly smaller rhino beetles, Strategus mormon and Strategus antaeus.) Riley narrowed down my find to either Dynastes tityus, commonly known as the eastern Hercules beetle, or Strategus aloeus, the ox beetle.
Ounce for ounce, rhinoceros beetles are some of the strongest animals on the planet. As a 1996 study famously found, they can carry up to 100 times their body weight. Alas, rhinos can’t compete with the bull-headed dung beetle, which can haul a mind-boggling 1,140 times its own mass. Entomologists tend to roll their eyes at these oft-cited factoids, since the beetles don’t, in fact, haul heavy loads on their backs in the wild. Instead, they likely evolved super strength so they can duke it out with each other (more on that later).
Rhino beetles are whoppers of the North American insect world, with males of some species reaching a maximum 2.5 inches in length. Both Dynastes tityus and Strategus aloeus feed on decaying wood, and the males of both species have horns, hence the name. The adult beetles are nocturnal, and since most people don’t go around busting open old, decayed logs, they don’t see the larvae either.
Without examining my grub under a microscope, Riley couldn’t say for sure which one I’d found, although he was leaning toward the ox beetle. He assured me that despite their fearsome appearance, adult rhino beetles are friendly, although their larvae can sometimes inflict a pinch. “They look ferocious, but they do not bite in any way, shape, or form and are not poisonous,” he said of the adults. “Their larvae are detritivores—they help process old logs into dirt.”
The adults are about the size of a plum and have two pairs of wings: a big, shiny outer pair that covers an exquisitely packaged second pair underneath. “Those hind wings unfold and rapidly beat, and that’s what gives them lift and power through the air when flying,” Riley said. The grubs, or larvae, develop from eggs laid in the dirt. They spend about a year in larval form, molting three times and growing larger each time. (Based on its large size, mine had likely already finished its last molt.) The larvae then enter the pupal stage before finally emerging as adults.
And those larvae? They look like something you might sizzle up in a skillet if you were hungry. In Texas, humans generally don’t eat grubs, but birds, raccoons, and possums might make a meal of one. In parts of southeast Asia and in the Amazon, people do eat grubs, which are high in protein. Riley has sampled them and gives them a middling review. “I’ve eaten a few beetle grubs that burrow in wood and they kind of taste like sawdust,” he said, noting that the ones he ate were fried in oil and resembled thick, crinkle-cut French fries.
Riley grew up in the Panama Canal Zone, where he and his brother spent a lot of time outdoors. Their parents collected butterflies, and Riley developed a deep appreciation for the local beetles, which grew to terrific sizes and flocked around flood lights at the local softball field. “Everybody would be watching a softball game and I’d be watching those beetles. Every now and then one would crash down, and I’d crawl under the bleachers to find it,” he said. Those insects, called Megasoma, or elephant beetles, make the ones in my Texas backyard look tiny. Full grown, they’re closer to the size of a baked potato than a plum and are covered with rust-colored fuzz. “They’re just impressive-looking beetles,” Riley said. “Big, gaudy beetles with horns are just neat.”
Riley referred me to another expert, entomologist and coleopterist (beetle scientist) Brett Ratcliffe, who retired in September from his role as a professor at the University of Nebraska. The author of a dozen books about rhinoceros beetles and the former curator of insects at the University of Nebraska State Museum, Ratcliffe once sampled an elephant beetle larva. “They’re the size of a Polish sausage and taste like rancid fat,” Ratcliffe said. “I don’t recommend it.”
Taste aside, Ratcliffe also has a fondness for rhinoceros beetles, which have been prized throughout time not only for their edible larvae, but for their beauty and impressive size. But why the horns on males of some species? I wanted to know. “That’s one of the burning questions today,” Ratcliffe said. “The males tend to use horns to battle other males—not for fighting for a mate, but for owning a feeding site like sap or rotting fruit. And if you own a feeding site you can then attract the females.”
Horns on rhinoceros beetles vary in shape and size. They’re also bigger on beetles that were better-fed as larvae. Worldwide, indigenous people have used the critters’ wing covers and brown or black horns to make necklaces and bracelets, and in some places the horns are prized as an aphrodisiac. In Japan, where there’s a long tradition of keeping insects as pets, rhino beetles are often kept by children (sometimes after being smuggled in by wildlife traffickers).
In the wild, rhinoceros beetles are facing challenges. “We are losing them very fast because of development in primitive areas where their habitat is,” Ratcliffe said. “We’re lessening the biodiversity of the planet because we’re destroying where these things live.”
You can help the rhinoceros beetle by leaving rotting stumps in your yard until they’re fully decomposed, Ratcliffe said. If you do find a giant grub, cover it back up and leave it alone. Turn off outdoor lights at night if you can. They draw beetles in, making them targets for birds or leaving them vulnerable to cars, which can squash them. “Have a general appreciation for creatures that share the planet with us,” Ratcliffe said. As for the larva I found in my yard, I never saw it again. Hopefully it’s still out there somewhere as a big beetle, patrolling the lawns and tree stumps of the neighborhood.