Just a bit of background: one of my favorite zombie causers is from the Dead Rising video game series. In it, the undead are reanimated by a wasp-like insect that lays eggs in a corpse (I think. It's been a bit). I always thought that was a cool gimmick if nothing else, but something wondrous happened in the third entry in the franchise. A variant of zombie was introduced that was covered in hives of stinging wasps. I thought that was an amazing visual and a great idea.

With that in mind, I've been trying to think about a wasp hive and zombie symbiotic relationship. From the wasps point of view, zombies are free food. Zombies just don't care about wasps. However, I can't think of an actual reason why wasps would put their nests inside a walking corpse that's prone to lunging at living humans.

What benefits would a species of wasp-like insects have to receive so that they make hives in walking-corpse-style zombies?

For the framework of this question, the zombie is a rotting corpse that's being animated by malevolent spirits. It can be intentionally created, but have a nasty tendency to occur naturally on "cursed land". The point is that long term evolution/adaptation on the part of the wasp is possible here.

Also, I'm going to check the box that says only humans can become zombies. That makes this hypothetical setting less awesome, but closes the lid on what would otherwise be a big can of worms.

Because it's a viable ecological niche, of course. The wasps are an evolutionary development of the Ichneumonoid wasps https://en.wikipedia.org/wiki/Ichneumonoidea which lay their eggs in living hosts, which the young then consume when they hatch.

For the wasps to become a hive species is an obvious evolutionary step. The hive controls the host ("zombie") so that it moves around to new food sources. The zombie lunges at other humans so that the wasps can form a new colony in the human. It's their form of reproduction.

Note that under this rationale the zombie isn't initially a rotting corpse. The wasps must parasitize a living human. The human eventually becomes something akin to a rotting corpse as the wasp larvae consume it from within. Which is part of the reason why the wasp hive is driven to find new hosts: eventually enough of the zombie is consumed that it just disintegrates.

PS: Having the wasps infect living humans gets around a lot of suspension-of-disbelief problems (IMHO, anyway) that come up when you try to reanimate corpses. I mean, unless your corpse is really fresh, decay has set in, so muscles and nerves don't work any more. Using living hosts just combines things that already exist in nature - the wasps, the zombie fungus, insects that lay eggs in humans...

PPS: And from today's news, it seems that parasitic wasps have been around for some time: https://www.livescience.com/63456-parasite-wasp-fossil-pupae.html

I cannot more highly recommend james answer! This was to the point exactly what I came here to say, the rotting body's and being driven to find new homes and nests and repopulate! It defiantly is the best idea for a motive when it comes to combining these two entity's. The only thing I could add at this point would be suggestions to make it cooler.

Honey has been found in old mason jars dating back hundreds or more of years and is a very good preservative. If you were to coat the the zombie in a hive or make the entire thing one, most muscles, bones and skin could be preserved for some time from the honey and from the wasps maintaining a shell from the actual brown hive material that they make themselves.

Honey crystallizes over time into sugar, which could be used as a more serious and stronger anti rot mechanism. By making the honey crystallize faster with special vomit or chemicals, which vomit is how they make honey as well so it could make sense. Maybe make that an evolutionary trait that more evolved wasp or bee hives use.

The honey coating the skin could also be used to infect people like a saliva from a bite would. It could have micro eggs inside that could hatch in the host, and enter them from small cuts or if it gets in their mouth, nose, ears, where ever it can infect. Making them highly dangerous and wanting to keep them at a range.

Lastly, Wasps and bees and other insects release Pheromone upon biting and stinging which act like a beacon to other wasps. This could be used to attract other zombies or just by drone wasps on the hunt for food which then alert the zombie & hive to where the person is.

This honestly sounds horrifying because you would be stung to death or eaten to death than reanimated as not just a dead guy but a dead guy with bugs full on living and thriving inside of you. That's just.... Words don't describe, it is scarier than some stories by Stephen king, that's for sure though!

Are you "traditional"?

I'm not sure how much change to the concept of zombies you will accept. I'm saying "current" because it can change: Compare "running" zombies, which apparently have been used quite early, but have been popularized by 28 days later to a point where nobody would consider that out of the ordinary anymore.

The Idea

What if on zombification, there's a short period where your zombie's flesh - or better, only certain body parts - "melts" onto things? So, a guy gets zombified, it is attracted to the noise/movement of a wasp hive, attacks it and from then on it "sticks" to the zombie.

The concept is more a quick idea right now and needs to be worked out a bit, but a small period that determines a zombies "job" opens up a lot of other possibilites, too.

Some possiblities

Just at the top of my head, going with the "attracted by sound" reason, I can think of some interesting variations: Think of a lawnmower zombie. Think of a jackhammer zombie. Think of beeping alarm clock zombie - which at first sounds a bit ridiculous, but not seeing any zombie and only hearing an alarm clock getting nearer is some good horror. You can even go for some comical relief with boombox zombie.

And apart from the "job assignment", you don't need a lot of fantasy to explain certain story events with it. Again, top of my head, what about a zombie plugging a sewage system, or some machinery?

jamesqf's answer is really nice I'd add just one other option to that; the wasps may also be getting a ride somewhere rather than just to the next food source. If the outside environment is hostile, like a city or a desert or similar, somewhere that water and vegetation are scarce and nonhuman hosts/prey are absent, then using humans as shelter and transport to a more hospitable location makes good sense. The human body is mechanically very good for moving through a wide variety of terrestrial environments and has a reasonable internal volume that can be taken over for breeding/sheltering without compromising the muscular structures needed for motion.