Dear 100 Hour Board,
Box elder bugs are weird.
I recently moved into a house with a couple of large box elder trees on the lot. This means that there are box elder bugs everywhere! After doing some light research I found that they pretty much don't have natural predators, and eat almost exclusively parts of trees in the Acer genus (with some exceptions for fruit.) As I was thinking about this today I realized how extremely unusual this is. They are obviously prolific breeders, and have no real threat from predation. But they are basically limited in number by their limited food source.
My question is two part. First, why? It seems like an animal like this, that is so free from predation would quickly change to be able to eat more kinds of things and then spread like wildfire. But that hasn't happened. Is there something about their diet that helps reduce the threat of predation?
Second, how many other animals do you know of that have such a limited food supply, and yet are thriving? It seems like most cases like this are animals that are struggling to survive, or gain obvious benefit from what they eat that reduces the chance of predation. The first group includes animals like giant pandas and koalas, while the second includes things like caterpillars, with the obvious example being monarch caterpillars, that store poisons and bad tasting chemicals from the plants that they eat to ward off predators.
This is an interesting question and one I would love to answer in a satisfactory fashion. Unfortunately, I am currently struggling to pass my classes and I won't be able to do adequate research until Christmas break. Would you want to ask it again then?