Thursday, July 7, 2016

Hercules Beetles - Rhinos, Unicorns, Oxen and Elephants

     The Eastern Hercules Beetle (Dynstes tityus) is the heaviest beetle in North America. This huge creature (up to almost 3 inches) goes by several other names as well: Rhinoceros Beetle, Unicorn Beetle, Ox Beetle, Horned Beetle, and Elephant Beetle for example, though other beetles are often better known by these names. The scientific Genus name is derived from the Greek for "lord" or "ruler" while the specific epithet refers to a Greek mythological giant Tityus. They certainly are impressive beetles. Members of the same family are also large and have all sorts of horns and projections. I've been lucky enough to come across a particularly large Elephant Beetle (Megasoma elephas) male, a close cousin, among the palm logs in El Salvador.

An Elephant Beetle we found among the fallen palm trunks in El Salvador.

     As large and heavy as they are, these beasts can fly. I remember one evening when I was manning a black light set up to attract moths and other insects. Everything at night seems a bit louder and more ominous, and I was actually a bit startled when I heard a Hercules Beetle come crashing through the bushes and crash into the hanging white bed sheet. It was as though someone had tossed a rock into the cloth.
     Male Hercules Beetles are larger and heavier than the the females. They have impressive horn-like pincers that they use to combat other males. Males often setup their territories on a rotting log (preferring ash trees) near the females which have attracted them using pheromones. They take on all challengers in their pursuit of a mate. They try to push, grab and shove each other off the log, holding on tight with their powerful legs. Whenever I find one, it always surprises me how strong a grip they can have. The largest and strongest males gain the opportunity to mate with any females who choose their logs to lay their eggs in their logs.

An Eastern Hercules Beetle grub and a females adult (note the lack of horns).

     Females lack horns. They lay their eggs into the rotting wood. The grubs that are born get to be huge in the two (sometime three) years it takes them to mature and then pupate. They feed on decaying wood, causing no harm to living trees. Despite the fearsome look of the beetles or grubs, and especially the huge pincers of the males, they are harmless to people.

A male Eastern Hercules Beetle, dark from being well hydrated and freshly emerged from the moist soil. 

     Adult beetles live for several weeks to a few months. They can vary quite a bit in coloration, with fresher and better hydrated beetles often appearing darker than older and more dehydrated ones. When buried in the soil, their shells seem to absorb moisture and darken. They typically have an almost velvety appearance. Adults feed on rotting fruits and sap. I've had fair success feeding them fruits with a bit of molasses on them. They seem to love the molasses and maple syrup that's been watered down just a bit.
     These beetles are always a thrill to find, and we use to have people bring them to the nature center I worked at every year, worried about these insects, and always happy to learn they are harmless and not garden pests. With the loss of mature forests and because they are negatively affected by light pollution that disorients them, they're not as common to find anymore. Their strength and size has resulted in their various common names, but regardless of what people call them, they're always impressed when they do find them.


  1. Leanne Wiberg - Naturalist at NOVA ParksJuly 8, 2016 at 8:51 AM

    This post had its beginning in Alonzo's response to a post I made to our naturalists facebook group. Yesterday, I posted a photo of a large male Hercules Beetle (a visitor to the nature center where work ) which had been brought in by a visitor. It was obviously dead. What was NOT so obvious was why it was attached to a tennis ball. Thanks to Alonzo and everyone else who responded. Just over 6 hours later, Alonzo published this post. Quick work!