Insect or animal that can live or shelter inside a living plant?

I've been trying to Google this one, but it's just a little too complex, I can't find a way to word it that turns up results.

Animals living in a hollow tree isn't what I'm looking for, it needs to be a living plant of some kind (though now that I've said that I realize some hollow trees are still alive. That's not too bad, but I'd like some other ideas). If I can't find any such thing, I might be able to use an animal instead (as the shelter). I know there's fish that swim inside a whale's mouth for a while and will clean its teeth, and that's pretty close, but I'd really prefer it to be a plant. Oh, and I don't want animals that live inside their parents, like a kangaroo in it's mother's pouch, it needs to be something of a different species. A hermit crab is somewhat close (If I have to go with animals living in other animals, or castoff parts thereof), but it really should be inside a living thing.

In fact, the absolute best would be an insect or small creature that can live inside a carnivorous plant.

In some ways a wasp laying its eggs in a caterpillar or spider is pretty close, but that kills the host, and I am definitely NOT looking for that. It needs to be either symbiotic or at least not harmful to the sheltering plant (or animal).

 

Tapeworms
There are some ant species that make their nests inside of plants and in return keep plant eating insects away

https://www.natureconservancy.ca/en/blog/archive/parasitism-the-dark-side-of.html

 

Did you look for "symbiotic relationships" between plants and insects?

 

Here's a real eye-opener from Wikipedia, about pitcher plants.


Feeding behavior
Foraging, flying or crawling insects such as flies are attracted to a cavity formed by the cupped leaf, often by visual lures such as anthocyanin pigments, and nectar bribes. The rim of the pitcher (peristome) is slippery when moistened by condensation or nectar, causing insects to fall into the trap. Pitcher plants may also contain waxy scales, protruding aldehyde crystals, cuticular folds, inward and downward pointing (retrorse) hairs, or guard-cell-originating lunate cells on the inside of the pitcher to ensure that insects cannot climb out.[1] The small bodies of liquid contained within the pitcher traps are called phytotelmata. They drown the insect, whose body is gradually dissolved. This may occur by bacterial action (the bacteria being washed into the pitcher by rainfall), or by enzymes secreted by the plant itself. Furthermore, some pitcher plants contain mutualistic insect larvae, which feed on trapped prey, and whose excreta the plant absorbs.[5] Whatever the mechanism of digestion, the prey items are converted into a solution of amino acids, peptides, phosphates, ammonium and urea, from which the plant obtains its mineral nutrition (particularly nitrogen and phosphorus). Like all carnivorous plants, they all grow in locations where the soil is too poor in minerals and/or too acidic for most plants to survive. Pitcher plants supplement available nutrients and minerals (which plants normally obtain through their roots) with the constituents of their insect prey.

Mature plants of Nepenthes lowii attract tree shrews (Tupaia montana), which feed on nectar that the plant produces but also defecate into the pitcher, providing nitrates and other nutrients. The plant and tree shrew have a symbiotic relationship. The rim of N. lowii is not slippery so that tree shrews can easily get in and out; it provides more nectar than other pitcher plants. The shape of the pitcher rim and the position of the nectar ensure that the animal's hindquarters are over the rim while it feeds.[6]

 

Thank you, that is fascinating stuff!! I hadn't thought of tapeworms. They're not generally considered benevolent or symbiotic, and aren't exactly warm cuddly creatures. I know I didn't specify warm and cuddly, but I'm looking for a metaphor or simile to use in a story—a rather complicated situation in which the MC takes shelter (her personality only) inside the body of another person who is affiliated with nature and especially plants. I really don't want associations of her with tapeworms or other parasites or creepie-crawlies that people consider revolting or pests.

That was in response to all the answers here, which are all intriguing and I thank everyone. But it didn't occur to me to write that I'm not looking for parasites or disgusting creatures. However, just writing the question, and now seeing these responses, has helped me work out an idea. I have my answer now, and it's actually far better than I thought it could be.

D'oh! I did NOT! even though I used that word above (that was after my attempt at searching).

Super cool! Parasitic insects living in carnivorous plants. If it wasn't to represent the MC I could definitely use that!

Spurred by these responses, I've now found that several kinds of insects indeed do live in various types of carnivorous plants. One is a spider, doubling the creep factor! Thank you @jannert, for doing some of my research for me.

I do have an answer now, so no more responses needed (if anybody wants to write more cool stuff about symbiotic relationships in nature, it could serve future seekers for similar questions though). Thank you all once again! It was only through the process of the thread that the answer came to me.

 

Either that one goes right over my head, or it's just entirely too English for me to understand...