Stag Beetle

2016 July 6

While we were camping at Traverse City on June 18, Sandy found this big black beetle trundling about[1]. It was pretty big, the body was around an inch long (about the size of the first joint of my thumb).


When aggravated, it would rear back with its mandibles open, ready to sell its life dearly.


The mandibles are very strong and robust, and cleary able to deliver quite a pinch given half a chance.


While in its threat pose, we could clearly see the pronounced yellow spots on its front legs. I don’t know if this is a useful diagnostic feature, though, because other people rarely post face shots of insects.


It didn’t actually get a chunk of flesh out of anybody, but it did pretty vigorously attack Sam’s hair.


It looks like Lucanus placidus, one of the darker beetles in the Stag Beetle family. Except for those yellow patches on its forelegs – I’m not seeing that feature in the BugGuide pictures. The species that has those patches is the Cottonwood Stag Beetle, Lucanus mazama, which I would be fine with, except that BugGuide only shows it living in the southwestern desert, not up in Michigan. Huh. Not quite sure what to think about that.

In any case, it is a male, because the females have significantly smaller mandibles. The males mainly use their big mandibles to fight with each other, but they clearly aren’t averse to useing them to attack other things if the need arises. The larvae live in rotting wood, and the adults are commonly found in “sandy areas”. Which the campground at Traverse City most certainly is – we were getting sand in *everything*.

[1] I didn’t have my good bug camera along, so we didn’t take all that many insect pictures at Traverse City. We do have another good insect specimen of a species that we never see in Houghton that I’ll be posting pictures of later, but you’ll have to be patient – we are raising it to adulthood first.

5 Responses
  1. Carole permalink
    July 6, 2016

    Have never seen one be aggressive.

  2. Lon permalink
    July 9, 2016

    If they like cottonwoods, that could be a factor, too. I don’t specifically remember cottonwoods in the Traverse area, but there’s plenty near the shore in Berrien County, and here far from the shore NW of Chicago, so I wouldn’t bat an eye at cottonwoods there. Unless a fluff got in my eye..

  3. July 10, 2016

    I wonder if anyone’s ever done force tests on those mandibles.

  4. July 12, 2016

    KT: Yes, they have. The force was measured at around 7 Newtons, which is quite high considering the small area of the mandible tips – more or less equivalent to applying 1.5 pounds of force to a pair of wire-cutting pliers. This would be a pretty substantial pinch, probably well over what is needed to break the skin.

    Mark Twain didn’t call them Pinch Bugs” for nothing!

  5. July 12, 2016

    Lon: There were definitely cottonwoods around Traverse City.

Comments are closed.