Many museums and universities use dermestid beetles to clean skeletons.
Also called skin beetles -- "dermis" is the Greek word for skin -- these insects feed off decaying carcasses and other organic material.
Adults are big enough to strip a skeleton relatively quickly when there's enough of them working on it, and dermestid larvae are perfect for cleaning tiny bones.
According to Stephen H. Hinshaw of the University of Michigan Museum of Zoology, the genus of dermestids known as Dermestes are really good for preparing skeletons because they reproduce well at room temperature. That makes it easy for a museum to develop and maintain its own beetle colony. Since Dermestes aren't able to fly at temperatures below 80 degrees Fahrenheit, their colonies are easy to control.
Also, dermestids don't like to eat feathers, fur, dried blood, most organs, or skin -- which is sort of funny, given their name. That means they're less likely to damage other specimens or exhibits that contain those elements. Hinshaw explains that dermestid beetles are easy to find -- just look inside some road kill or other animal carcass. Dermestids need to be kept in a hard container with smooth sides and a lid to prevent them from climbing out, and they normally won't eat anything that's been preserved in formaldehyde, because it's poisonous and will kill them.
Once a colony is established, these bugs can be used in many ways. They're often put to work cleaning dried carcasses, but they'll also eat fresh meat, and a big enough colony can clean off a small freshly killed creature overnight. Bigger pieces, like a large predator's skull, take longer to clean and will probably start to spoil before the beetles' job is done. Not that the bugs mind, but the smell can get pretty bad!