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Bark Beetles With Identity Issues: Reclassifying the Cryphalini

Pygmy borer beetles

The former Cryphalini, now spread among three tribes, are all rather tiny. Here are six species compared to a grain of wheat (bottom): top row, left to right: the coffee berry borer Hypothenemus hampei, the erudite pygmy borer Hypothenemus eruditus, and Trypodendron domesticum; second row, left to right: Eidophelus darwini, Ernoporus parvulus, and Cryphalus dorsalis. (Image by Jiri Hulcr, Ph.D.)

By Jiri Hulcr, Ph.D.

Do you know that the most common bark beetle on Earth probably lives in your backyard?

I am sitting on my porch typing on my laptop, when a tiny bug flies up and I catch it. It is a pygmy borer: Hypothenemus eruditus. The “erudite pygmy borer,” described from a specimen chewing on the binding of a book in an old English library, is tiny, 1mm long, peach and chocolate colored, and fuzzy. It is as common in my yard in Florida as in Papua New Guinea.

So why isn’t a beetle like this in every backyard bug guide? One reason is that it has had identity issues.

The pygmy borer genus Hypothenemus belongs to the megadiverse tribe Cryphalini. Well, used to, until today. When Steve L. Wood and Don Bright, the founders of modern bark beetle classification, published the famous catalogs of bark beetles in 1980s, they threw up their hands over the Cryphalini and proclaimed them hopelessly chaotic.

Not anymore! Andrew Johnson, Ph.D., and collaborators have just fixed the Cryphalini. This taxonomic monument, published this month in Insect Systematics and Diversity, is the biggest bark beetle reclassification act since Wood and Bright’s heyday.

For bark beetle taxonomy buffs, the real meat of this tome is the creation of three new tribes, three new genera, more than 250 other taxonomic changes, and the 120 target-capture genomes that support this work.

For the rest of the world, the interesting stuff is in the details of these beetles, which are more surprising than science fiction. For example, one genus practices obligate inbreeding: sex between a brother and his sisters. And how about food? Johnson, assistant research scientist at the University of Florida’s School of Forest Resources and Conservation, spent months cutting up the stomachs of these minute beetles to look for diagnostic characters, only to discover that one of them does not have a stomach! What does it eat? Nobody knows.

And why should you think of these tiny beetles every morning as you are sitting down to your coffee? Because the coffee berry borer, another Hypothenemus, traded life in bark for boring into seeds and became the world’s biggest pest of coffee.

For the first time we have clear names for these bizarre pygmy borers. But also for the first time, we can admire their beauty. Our specialized imaging system allows us to capture these beetles with the resolution of an electron microscope while maintaining the vivid, live colors. Dig into the reclassification of Cryphalini and see for yourself.

Jiri Hulcr, Ph.D., is an associate professor with the School of Forest Resources and Conservation, University of Florida, Gainesville, Florida. Email: hulcr@ufl.edu

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