Blood-Colored Checkered Beetle

2022 March 27

Sandy found this tiny red beetle on her hat on March 23, 2022. It was just about the size of a grain of uncooked rice (short-grain, not long-grain). She caught it under a drinking glass to save it for me until I got home from work.

When I flipped it upside down on a smooth piece of tile, it couldn’t get a purchase to flip itself back over, so I got some pictures of its underside.

This looked familiar, and checking back on my previous postings I found that I had photographed one of these back in April of 2012, almost exactly 10 years ago. Of course, that was before my big macro lens upgrade, so I got considerably sharper pictures this time.

It is clearly a Blood-Colored Checkered Beetle, Zenodosus sanguineus. These are not only the only member of their genus, they are also the only member of their subfamily. Their blood-red color makes them extremely noticeable, which is why they are one of the hundreds of species described by Thomas Say back in the 1830s.

Now that I’m getting the hang of managing the lighting for the MP-E Macro lens, I’m getting quite fond of it. We can actually count the individual elements in this tiny beetle’s compound eyes, and in the next picture we can see fine details of its antenna and front foot. Keep in mind that the antenna there is smaller in diameter than a single human hair.

These beetles are reported to be predatory, and normally live in rotting stumps and logs where they hunt down wood-boring insects and all the other small arthropods that live in that environment. Based on the color, I have to think that these are probably either highly distasteful or screamingly toxic.

I expect that this beetle is part of one of the local Mullerian-mimic complexes. Mullerian mimicry is where a toxic insect evolves to resemble other toxic insects, so that when a predator tries to eat one of them, it learns to avoid all of them. So, around we have all these insects that taste bad and/or are toxic to eat, and have adopted orange-and-black as their warning colors. This includes Monarch butterflies, milkweed beetles, milkweed bugs, box-elder bugs, this beetle, and a few dozen or so others.

There also appears to be a second mimicry complex around here, where insects are trying to resemble yellow-and-black wasps like yellowjackets and paper wasps. This is partly Mullerian mimicry, and partly Bayesian mimicry where non-stinging insects try to trade on the reputation of the stinging insects. So, the black-and-yellow insects are likely to sting, while the black-and-red/orange ones are likely to taste ghastly.

And by an odd coincidence, the school colors for Houghton High School (which my kids go to) are black-and-orange, while the colors for Michigan Tech University (where I work) are black-and-yellow. So I guess the high school is advertising that they taste bad, while the university is threatening to sting.

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