No, the blighters eat any wool. I had them a few years ago, and I think they came in with some knitting yarn I bought in a charity shop - either that or through the plaster behind a loose bit of skirting in the upstairs loo. I realised what they were when they chewed through the yarn and I saw one making a beeline for it.
At first I thought they were bedbugs, which was awful. They are nothing like bedbugs, but I didn't know that, and bought a mattress hoover, a zipped cover and various sprays. I'm shuddering just remembering it. I read obsessively about them, and they do come in from outside, and even an open window is an invitation. They like bedrooms as people are less likely to move the furniture to vacuum than they are downstairs. Regular and thorough vacuuming is the way to go, I'm afraid.
I got something called Diatomaceous Earth Powder (available on Amazon) and sprinkled it around where the walls joined the floors. That stops them getting in from outside and is easy to apply. In the end, we decorated upstairs and replaced all the carpets anyway, but they'd gone by then. I recommend a hand-held vacuum if you don't have one already (cordless is easier) and if possible move furniture so that you can get behind it, then hoover as often as possible. The powder won't do any harm, either, but I think you need a vacuum with a HEPA filter to suck that up, as it would clog a regular one.
