("Bad Bug")

Written by Jonathan Wojcik, Researched and Translated by Rev Storm

Another simple one today; the name quite simply means "bad bug," and its description calles it extremely wicked. It is said to swim freely around the body with its flexible torso and tail fin, and uses its six sharp claws the stab the victim's spleen. Whatever the host eats, Bad Bug will steal by "sucking out the essence" with its pointed mouth.

Design Review:

Wicked though it may be, Akuchuu is one of the cutest in the book thanks not only to those little round eyes but the fact that its wiggly, pointed proboscis ends up looking like one of those fuzzy worm toys. Aesthetically the pale maggot-like body with red extremities is a very cool look as well, reminiscent of Gyoshuu from our first entry as well as some other, upcoming bugs!


Akuchuu is so vague that it could practically be any parasite in the world, and it probably isn't meant to be one in particular. It does, however, have a very distant doppelganger in the animal kingdom, by which I mean there is precisely one internal parasite us humans can contract that actually does, in fact, possess clawed legs.

That's because a Pentastomid isn't just some sort of "worm." Covered in a chitinous exoskeleton, we're reasonably certain that this parasite is an arthropod. An arthropod that has evolved a life cycle strikingly similar to that of the tapeworms we looked at over the last few days.

What you're seeing in these photos are the microscopic larvae, which in this species possess just four legs and a sharp tail, but there are indeed some which possess six legs. So they're insects, right? Nope! Nothing else about their anatomy matches the Insecta, and it's currently believed that they're a group of Crustacea, though even a relationship to tardigrades has been proposed in the past.

Just like a tapeworm, pentastome larvae break out of their first host's stomach after being ingested as eggs, and encyst themselves somewhere in the host's flesh. This first host however is most commonly a fish, and the intended second host of most Pentastoma is a bird or a reptile, though several species favor mammalian predators. It does not, however, pass through the stomach and into the digestive tract, but uses those lovely little claws to climb from the esophagus and into the respiratory tract. Within the lungs, the little crawler molts several times, loses its legs entirely and matures into a blood-sucking, tubular adult that, in some species, resembles a flattened tongue enough to simply be called a "tongue worm," while in other species the adult stages have this beautiful, corkscrew-like "spinal column" shape.

No known species of Pentastomid naturally infects humans, but several species infect dogs in certain parts of the world, and accidentally make the jump to dog owners with some regularity. HERE you can read a detailed paper on pentastoma found in a man's heart, and HERE is an account of one clambering around in someone's eyeball. Just like tapeworm larvae, they tend to get confused in a human body and wander around a little too much for their own good.

It feels especially unlikely that the creator of the Hara no Mushi could have ever seen a pentastomid or even speculated on their existence, but isn't it wonderful that so many parasites exist in this world, we can still find one to match with every one of these critters thus far? Enjoy it while it lasts, since a couple to come are far too abstract for that to work out!