Horned Passalus

This bug loves to eat wood. But don’t worry, your house isn’t on the menu (finally).

Meet the horned passalus, Odontotaenius disjunctus, commonly known as a betsy beetle or bess bug.

This beetle plays an important role in decomposing dead trees, but it has no interest in living trees or the lumber in your home (assuming that the lumber’s in reasonably good condition, anyway.)

Florida residents will occasionally encounter the horned passalus crawling about in the open. It’s easily recognizable due to its large size (about 1.5 inches long) and its coloration, which is very black and very shiny.

How black? How shiny?

Let’s just say that 1930s-era Cadillacs and U.S. Marine Corps dress shoes probably break down and weep with envy when a bess bug passes by.

Not that this species particularly needs a super sweet paint job to get along, you understand.

In its larval form, the horned passalus is a big, soft, white grub. It lives within the galleries that its forebears have chewed through decaying logs when they were young, carefree adults. The grub feeds on frass (a fancy word for bug poop) that its forebears dropped in the galleries. Adults occupying the same log will even work together to protect each others’ grubs, in the name of group solidarity.

Do-it-yourself types sometimes encounter horned passalus grubs while cutting up old logs to prepare them for the trash collector. Or they see the adults ambling around woodpiles or under logs.

Unfortunately, there’s not much that can be done to help a grub that’s suddenly been exposed to the harsh light of day in that situation.

Though one BugWeek Web Team staffer points out that every cloud has a silver lining….

“A few years ago I was cutting up the trunk of an old dogwood tree that had been sitting around the backyard for too long.

“When I split open a section of it, I found a huge grub. I assumed it was a bess bug larva, just based on the size of it.

“There was no way to repair the damage to the tree trunk, so there didn’t seem to be anything I could do to help the larva.

“However, there was a big female golden web spider in my yard, and I decided to give her a treat.

“I tossed the huge, fat grub right into the spider’s web. The silk was strong enough to hold. The grub began squirming around obligingly, which got the spider’s attention. And for a couple of minutes that spider kind of stood by and watched, apparently uncertain what to do about this mysterious windfall.

“Finally the spider seemed to accept that this was a food item, and she got down to business eating it. It took a long time.”

So, let this be a lesson to all you humans out there – once in awhile, there really is such thing as a free lunch. But don’t kid yourself, somebody ALWAYS ends up paying for it.

You can read more about the horned passalus, at this “Featured Creatures” document prepared by the UF Department of Entomology and Nematology.