Hungry Hungry....Hippos?

Ever find little furry, brown larva eating away at your cottons? Or see the aftermath in the form of tiny holes in the most inappropriate places on your favourite T? I've unfortunately found them on my woolens, cottons, and even my papers. I clean! I wash! I vacuum! But these devils refuse to permanently leave. Just when I think they're gone for good, I'll find a new hole somewhere.

There's nothing new in that. However, I thought they only devoured natural fibres including my sheepy moccasins for those cold, wintery floors. I'd never seen them eating any polys of any sort yet today, I found them in the strangest place: on the thin styrofoam sheet that protects a mug of mine inside a box. And indeed, they'd eaten a number of holes in it. Are they mutating? Or is this a new form of styrofoam that includes natural material suitable for recycling? Is nothing safe from these insects?? And why can't I get rid of them?!?!?