Beetle Bites – Ripiphoridae are Probably Eating your Insides Right Now

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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.

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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.

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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.

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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.

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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.

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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.

Overview:

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.

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