If one thing is true about human beings, from the Mayans to the Chinese to the Celts, it’s that we just can’t help decapitating our enemies and putting their disembodied heads to “good” use. Certain peoples believe the heads provide spirit to the community, others use them to intimidate their foes, and still others shrink them and keep them as souvenirs. Even Disneyland has an animatronic head called Shrunken-Head Ned, because nothing quite says family values like ritualistic decapitation.
Meanwhile, the aptly named assassin bug looks on and wonders what all the mercy is about, for this insect impales its prey and sucks it dry, then attaches the entire corpse to its back. Not just one or two at a time, mind you—these bugs can be found lugging around massive piles of their foes. Burdensome and unnecessarily sinister, it would seem, but this functions both as visual and olfactory camouflage as well as highly effective armor.
There are some 7,000 species of assassin bugs the world over, and while not all engage in this remarkable behavior, each is equipped with nasty, highly hardened mouthparts called a rostrum. With this the assassin bug stabs through the exoskeleton of its prey—ants and termites and bees and such. An outer sheath peels back once inside to expose the maxillae (mouthparts used for chewing) and mandibles, according to biologist Christiane Weirauch of the University of California, Riverside.
They then inject a toxin that paralyzes the victim in a fraction of a second and begins liquefying its innards, as a spider would do to its prey. “Essentially they make the hole,” Weirauch said, “they hook the mandibles in, they inject the stuff, then once the victim stops twitching they can insert the maxillae even a little bit farther and then start slurping up the contents.” It’s all quite a bit like that bug from Starship Troopers drinking that guy’s brains (link is NSFW, obviously, unless you work at the Official Starship Troopers Fan Club, in which case, kudos to you for not giving up on the things you love).
Then, utilizing a sticky secretion on their exoskeletons, some species will pop the corpse up onto their back. Exactly how they do this is a mystery, according to Weirauch, given that they can’t reach their back any better than humans can lick their elbows. But in addition to the pile acting as camouflage from predators, Weirauch says: “What happens when a gecko tries to capture one of those, is it might actually end up with a mouth full of ant carcasses rather than a juicy assassin bug.”
The camouflage actually works the other way around as well, helping the assassin bug avoid detection by the critters it hunts. A species that goes after termites, for instance, will cover itself in their nest material to not only blend into the surroundings, but also to assume their scent.
Yet even more brilliant is this species’ hunting techniques. Like ants, termites practice what is known as social immunity, removing dead or dying comrades from the colony to avoid outbreaks of disease (and sadness, possibly). “And the assassin bugs seem to be taking advantage of that, in the sense that they would capture one termite, suck it dry, and then have it dangle from their rostrum into the termite mound and lure the next termite that way,” Weirauch said. One observer, she noted, witnessed an assassin bug use this trick to capture 48 termites in a single sitting.
Still other species turn themselves into veritable flypaper by excreting sticky goo onto their forelegs to help them snag prey. Others harvest resins from plants for the same purpose. And that’s particularly remarkable, because it comes damn close to actually being a kind of tool use. (Interestingly, as far as insects go there is in fact a wasp that grabs pebbles with its mouth and uses them to tamp the soil where it’s buried its eggs. And it was probably doing it long before our ancestors figured out that stones hurt when you throw them at something's head.)
But why steal plant goo when you can harness the power of the millipede? Some assassin bugs exclusively target the many-legged critters, which release a noxious secretion to ward off predators. (Hilariously, lemurs exploit this by chomping down on millipedes and getting high off the toxins.) This doesn’t seem to bother the assassins in the slightest—they even release similarly powerful toxins from their own defense glands.
Weirauch learned that the hard way while collecting specimens from a light trap in Cameroon last year. “For some reason I touched my neck, and that burned like crazy,” she said. “So there must be some substance in those defense glands in these millipede-feeding assassin bugs that make them a lot more obnoxious than your typical assassin bug defense gland, and we're suspecting that there might be sequestration from the millipede chemicals happening there.”
Now, apart from occasionally delivering a painful bite, assassin bugs are usually no real threat to humans. Save for one group: the blood-sucking kissing bugs, so called because they typically bite humans painlessly around the mouth while we sleep. But if they happen to defecate in the process, protozoans from their feces get into the wound, leading to chronic heart problems that may only manifest decades later. Chagas disease, as it’s known, is a serious issue in South America, where substandard housing leaves more points of entry for the bugs, though infections may now be on the rise in the U.S.
Charles Darwin himself battled kissing bugs in South America—indeed, it’s been suggested that his illness beginning in 1839 may have been due to such bites. Apparently not disgusted enough by being assaulted while sleeping, he later used a kissing bug as a party trick. In his Beagle diary, he describes catching one, and “being placed on the table and though surrounded by people, if a finger was presented, its sucker was withdrawn, the bold insect began to draw blood.”
We must appreciate, though, the staggering diversity of the assassin bugs, which millions of years ago took a basic body plan and evolved it into a wide array of specialized physiologies. Whether it’s hunting termites or ants or millipedes, these assassins have adapted marvelously for the job.
I reckon it’s only a matter of time before they get their own attraction at Disneyland. Create an animatronic one and call it Corpse-Back Jack, maybe. Man, Shrunken-Head Ned is gonna be pissed.
Browse the full Absurd Creature of the Week archive here. Have an animal you want me to write about? Email matthew_simon@wired.com or ping me on Twitter at @mrMattSimon.
