It's a caterpillar invasion

There is somewhere in my house and/or yard that is breeding caterpillars. Cooper has discovered this place though, and is bringing caterpillars into my house regularly over the last three days. Sometimes the caterpillars are alive, sometimes they're not. Sometimes we have to pull them out of his mouth, sometimes he leaves them on the floor for us to discover.
Tonight, I found a very active little caterpillar dude upstairs in my bedroom. Cooper brought my attention to it by jumping and bouncing around it. I picked it up with a tissue and took it downstairs, dropping it in the flower garden outside. I don't really mind caterpillars per se, but crawling things creep me out when they're in my house. I wonder where this treasure trove of caterpillars is. I wonder maybe if they're at the base of the fruit tree? Because that's the only place that Cooper can get into. The rose garden is fenced off so he can't get into it. But do caterpillars set up camp at the base of fruit trees? I guess I'll check that out tomorrow.