Many naturalists will relate to this post: as nature enthusiasts, everyday tasks sometimes end up taking much longer than expected due to fascinating biological distractions just beneath our feet.
As I was mowing the front lawn over Memorial Day weekend, I stumbled upon a prehistoric-looking stag beetle, which is always a neat creature to come upon. As an entomologist, my first instinct was to pick it up to make a closer examination. Typically, I run into stag beetles a few times each year and it’s usually the large, “reddish brown stag beetle”: Lucanus capreolus (see image below). The beetle I found was a bit smaller, darker, and lacked the bicolored legs of L. capreolus, but was still a good-sized insect at over an inch long. After a beverage break and some Internet browsing, I figured I must have been looking at the closely related Lucanus placidus. Interesting, I thought, and placed the stag beetle back on a portion of the lawn that had already been mowed, lest it face the wrath of a metallic tornado.
Another pass or two with the mower and I spotted a few more stag beetles. I was no longer simply stumbling upon these beetles—something else must be going on. Once again, I stopped mowing to take a closer peek in the taller grass, only to find even more beetles. Within the span of five minutes, I had found nearly forty stag beetles in the lawn near a low spot where a tree must have previously stood. As with the first specimen, I gently relocated these beetles and rushed to finish mowing in the dwindling light.
Around 10:30 PM, I wandered back outside with a flashlight to see what the beetle situation looked like. I had no idea what I was about to stumble upon—hundreds of battling stag beetles! Male stag beetles use their large mandibles to compete for females, which made my front lawn seem like a combination of the Bachelorette mixed with Gladiator. It was astonishing to see the sheer numbers of stag beetles present in a single spot at a given time. In an attempt to count them, I starting placing them into an empty flower pot. The forty I had spotted earlier seemed like a drop in the bucket—quite literally! The bucket was nearly full to the brim with 250 beetles, and I eventually stopped counting. I’d estimate that I spotted nearly 400 stag beetles in a single night.
I did eventually confirm that the species of stag beetle in the lawn was Lucanus placidus. According to the scientific literature, aggregations have been noticed in lawns on occasion. In Kriska and Young’s “Annotated Checklist of Wisconsin Scarabaeoidea” (2002) an aggregation of 15 males and females was once noted beneath a black oak tree in the state. I’m not entirely sure what kind of tree used to occupy the low spot in my front lawn, but the stag beetles obviously loved it (note: stag beetle larvae live in decaying wood). As an interesting side note, the same low spot was also home to the “Dead Man’s Fingers” fungus (Xylaria polymorpha), another biological curiosity in its own right.
It’s amazing what you can find in your own back yard or front lawn if you take the time to look!