Case-bearing Clothes Moth
Image source: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org
Whilst there are a number of insects that will attack woollen carpets and clothes this now seems to be the most prevalent. Signs of infestation include irregular holes appearing in woollen clothes and carpets and what appear to be long grain rice type larval cases amongst the food source.
These are cases constructed by the larvae from frass and webbing and they are carried by them as they move through the carpet. A treatment with a residual insecticide will clear an infestation and Hillbans Pest Control offer a guaranteed service in most cicumstances. This insect will absolutely not infest synthetic carpets.