Darwin and Panagaeus

Much like the Dutch Tulip Craze or Beatlemania[sic], fashions have rocked the insect world since humans flipped over their first rock. One European beetle of note, Panagaeus, was the object of much veneration, which persists even into modern times. Indeed, Panagaeus is a member of one of the most relevant and interesting collection of organism on earth: the one I study.

Panagaeus cruxmajor. Photo: Kirill Makarov

I think these little dandies are just swell! But don’t take my word for it:

To this day, Panagaeus is to me a sacred genus. I look at the Orange Cross as the emblem of Entomological Knighthood.

-Charles Darwin, 1836

Darwin was also fond of recounting a tale from his youth about this same genus.

I must tell you what happened to me on the banks of the Cam in my early entomological days; under a piece of bark I found two carabi (I forget which) & caught one in each hand, when lo & behold I saw a sacred Panagæuscrux major; I could not bear to give up either of my Carabi, & to lose Panagæus was out of the question, so that in despair I gently seized one of the carabi between my teeth, when to my unspeakable disgust & pain the little inconsiderate beast squirted his acid down my throat & I lost both Carabi & Panagæus!

-Darwin, 1887

What makes Panagaeus so special? I’m not exactly sure. They’re one of the only carabids that produce phenols in their defensive sprays. Some are adapted to feed on snails. They among the most xeric habitat tolerant carabids known.

Panagaeus fasciatus. Photo: Henri Goulet

Ultimately, there’s some ineffable quality to these beetles that just sets them apart. What that is, I don’t know…


I’ve sequenced a Panagaeus transcriptome, as part of a larger phylogenetic project, in hopes of understanding what that quality is. While analyses are still ongoing, I’m optimistic they will yield pieces that will be useful in resolving the Carabidae family.

Or if that fails, at least they look cool on T-shirts.

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Darwin, C. (1887). The Autobiography of Charles Darwin. Barnes & Noble Publishing.

– (1836). Letter 299: Darwin, C. R. to Fox, W. D., 15 Feb 1836; reproduced in Burkhardt, F. and Smith S. 1985. The Correspondence of Charles Darwin, Volume 1: 1821-1836, pp. 491-493. Cambridge University Press, Cambridge.

Beetle Serial Killers: Promecognathus

This is Promecognathus crassus, a carabid beetle with one purpose in life: wrecking millipedes. Day in, day out, Promecognathus roams the forest floors of the western US in search of helpless millipedes, murders them, devours the remains, calmly reflects on the fragility of life, and repeats the process.

Millipedes are known for being nature’s chemical anarchists, producing many noxious compounds to ward off predators. These substances include alkaloids, cardenolides, quinones, acids, and hydrogen cyanide. Scary as this cocktail sounds, millipedes are generally peace-loving creatures, and as far as I know, no person has ever died from interacting with one (though they might stain your fingers if you’re reckless).

Consider yourself lucky.

However, if you were to, for whatever reason, eat nothing but millipedes for the rest of your life (fad diets, am I right?!), you would likely beg for death’s sweet release.

So how does Promecognathus manage to gorge itself on millipedes despite all those toxic chemicals? Surely these beetles have evolved a tough digestive system or some enhanced metabolic pathways to detoxify their prey, right?

Turns out the answer is no. Hydrogen cyanide and quinones will liquefy the insides of a Promecognathus, same as the rest of us. The beetle’s secret to avoid an agonizing death is all about technique. And those jaws.


Promecognathus sneaks up on the millipede and delivers a swift bite between the poor critter’s protective carapace, severing its nerve cord and rendering it paralyzed. The incapacitated millipede is unable to protect itself, and Promecognathus has its wicked way. I assume this behavior was the inspiration for the best Jet Li movie of 2001.

Why does the beetle bother going through so much trouble for a meal?  Millipedes presumably taste bad even without the toxins. Simple: millipedes are big, really abundant, and nobody else is eating them. Every time a clever and seemingly impenetrable defense evolves, some  creature will find a goofy way to exploit it.

So next time you’re hiking in the Pacific Northwest, you may just encounter a Promecognathus on the prowl, so keep an eye on the ground.

And watch your back.

Long Live the Queen: Eusocial Beetles

Here at BeetleFacts.org, we don’t beat around the bush when it comes to our favorite group of insects. Consequently, it’s easy to forget that other people can find non-beetles to be just as interesting. While I personally believe that these individuals are mistaken, and the very notion to be incomprehensible, I’m perfectly willing to admit that there are some neat groups of insects out there.

Take the industrious Hymenoptera. This order, containing bees, wasps, and ants, features some of the finest examples of social behavior and teamwork in all of Insecta. We’ve already brought you beetles that prey on bees. There are even quite a few beetles that actually look like bees, ants, and wasps.

Mimocolliuris chaudoiri. Photo: Alexander Anichtchenko

But these are just pale imitations. Every time I evangelize about the charm and splendor of beetles, I hear some dissenting voice say, “That’s great, but they’re not as cool as bees or ants. Those guys live together and have queens and workers, and make honey or little fungus farms, and they make awesome nests.”

This constant mockery once fueled my desire to invent a new species of eusocial beetle, using next-generation DNA technology and sinister occult rituals, which in turn brought on accusations that my research was “misguided,” “delusional,” and “reprehensible and most likely illegal.” While the National Science Foundation is entitled to their own opinion on my work, I believe that kind of language is inappropriate for a rejection letter. And there were many letters.

So imagine my shock and joy when I found out that nature had done my work for me. Behold, Austroplatypus incompertus, the first and only known eusocial beetle!


Not only do these beetles have reproductive and worker castes, they, like other species of ambrosia beetle, cultivate fungal gardens as a renewable food source. Suck it, ant nerds!

Formally described in 1992, A. incompertus live inside of Australian Eucalyptus trees, where they dig happy little galleries in the wood to make room for their larva and fungus. The queen beetle begins a new nest by finding a suitable tree, burrowing through the bark and into the underlying tissue, and laying a small clutch of eggs. After the larva hatch and mature into adult beetles, the male offspring escape into the wilderness, and the females loose some of their tiny beetle feet and stay behind to help the queen. These females dig more tunnels, defend the nest from intruders, and tend to the fungus while the queen simply revels in a pile of fungal spores like the plutocrat she is.

So the next time you believe there’s something amazing that beetles can’t do, just remember: there are more than 400,000 species of beetle out there, and one of them may just surprise you.


Where do Chlaenius live?


Short answer: Everywhere.

Long answer:


Okay, so what exactly are we looking at here? Each row shows the distribution and the number of species within all the different subgenera of Chlaenius . What is Chlaenius? Good question, but that’s a topic best left for another day. You’ll notice a few trends: Lots of diversity in Africa and Asia, very little in South America and Australia. Plan your next vacation accordingly.

Mystery Beetles – Zambian Panagaeines

Hey beetle folks: Anyone familiar with the Panagaeines of southern Africa? I’ve got a handful of specimens from Zambia that I can’t seem to get a confident genus name. I’ve got a guess, but I’d like to get some unbiased second opinions.

They were collected in Copperbelt Province during October and November by Kelly Miller’s lab. My hunch is that they’re three different species, but I wouldn’t be shocked if 1 and 2 ended up being conspecific.

I’m also not certain on their sex either. How? Am I really that terrible of a morphologist?

Maybe, but these fellows have a surprise that has thwarted my meager abilities: All of them have dense seta on all of their tarsi. Males of the average carabid have this feature on their front legs, presumably for clinging on to females during mating, so it provides a handy way to sex them in the field (or when you’re too lazy to sharpen your forceps and dig out their sexy bits).

Not these jerks. Their tarsi are as fuzzy as can be. It’s apparent even in my awful pictures. This isn’t a super rare condition in the beetle world, but it does suggest something more is going on with these Panagaeines. Do they have to cling to their prey, like some millipede or snail specialists beetles?

I’m interested to hear your thoughts and speculations.

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Upside down:

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Beetle Bites – Ripiphoridae are Probably Eating your Insides Right Now


Ripiphorus diadasiae (Photo: NoahElhardt – wikipedia.org)

If you were only judging from the common name, wedge-shaped beetles, you might conclude that ripiphorids were another pointless branch of the already overcrowded Tenebrionoidea tree of life.

You would be mistaken.

Ripiphorids superficially resemble the hunchbacked mordellids; in fact, the first described ripiphorids were initially placed in the genus Mordella, and there is relatively good morphological and molecular evidence that these two families (plus Scraptiidae, Melandryidae, and maybe a few others) are closely related. Unlike the dandy mordellids, ripiphorids aren’t content with playfully tumbling off of flowers; they’re out for blood.


Ptilophorus fallax (Photo: K.V. Makarov – zin.ru)

Ripiphoridae (not to be confused with Rhipiceridae, an unrelated beetle family that also contains weird parasitoids with silly antennae) is a relatively small family, with about 400 known species. They can be found worldwide, and while they tend to prefer warmer climates, you can find ripiphorids in temperate localities like Canada and the UK.


Pelecotoma flavipes (Photo: Tom Murray)

Regrettably for the host, this process is not fatal, and the nightmare continues once the newly emerged larva latches back onto the insect’s body and continues to feed on it for another couple of months before pupating. Only then is the host allowed to die, all while the pupa sits and matures, nestled snuggly against the withered corpse. I didn’t feel like writing a joke about children moving back in with their parents at 25, but you’re welcome to do so on your own time.


Ripiphorid larva on the wing of a braconid wasp (Photo: István Mikó)

In southern Florida, you can find an as-of-yet unnamed species of the genus Piridius that looks like someone glued a horsefly head to the body of a deformed bumblebee (check out some of Kyle Schnepp’s images of this beast here: http://bugguide.net/node/view/944505). Interestingly, this species was discovered a while ago (it’s been known since at least 2001). This kind of thing happens with surprising regularity in taxonomy: making sure that a species is really new to science takes time and effort, as does the actual act of writing the description, so it’s understandable that many hapless beetles fall through the taxonomic cracks. With any luck, it’ll get an epithet like ignorum or neglectens.


Macrosiagon bimaculatum (Photo: K.V. Makarov)

New species aside, Piridius is strange even by ripiphorid standards. They have non-functional, vestigial mouthparts that render them incapable of eating as adults (I’m actually a little surprised that any ripiphorid adults have functional mouthpart given their short adult lifespans. Seriously, why bother? They’ve just finished sucking the last dregs of life out of a poor host insect, which, don’t forget, they’ve already exploded out of once. Is that not enough living, you fithy heathens?).

It’s also a member of the enigmatic subfamily Ripidiinae, which is characterized by pronounced sexual dimorphism (at least in the few species where both male and females are known). The males are a bit on the thin and spindly side, as beetle go. The females, however, aren’t just odd looking; they’re barely recognizable as beetles.


Illustration from Batelka, 2009

As you can see, they’re goofy looking pouches of flesh with six legs poking haphazardly out what’s generously called the creature’s thorax.

The females of Piridius are currently unknown, but they’re probably similar to above illustration and, obviously, quite good at not looking like a ripiphorid. If I saw one, I’d just assume it was a mealy bug and probably toss it into the garbage or just squish it for fun save it in 100% EtOH for future study.


400 species in about 40 genera.

Arnett, Ross H., et al., eds. American Beetles: Polyphaga: Scarabaeoidea through Curculionoidea. Vol. 2. CRC Press, 2002.

Batelka, Jan, et al. “Two new ripidiine species in Dominican amber with evidence of aggregative behaviour of males “frozen” in the fossil record (Coleoptera: Ripiphoridae).” European Journal of Entomology 108.2 (2011): 275-286.

Batelka, Jan, and Jiří Hájek. “A taxonomic review of the genus Eorhipidius (Coleoptera: Ripiphoridae: Ripidiinae), with descriptions of three new species from Asia.” Acta Entomologica Musei Nationalis Pragae 49.2 (2009): 769-782.