Hi Jorge,
 
I just wanted to add to what Paul wrote about dermestid beetles. Be very
careful about not letting them loose into your collection area. If you begin
to find fine "powder" in your specimen trays or find any shed larval skins
(these look yellowish-brown in color and are bristly), you have some active
larvae eating away at the dried animal matter remaining in the shells. They
will also eat opercula, periostracum, and even your data slips. Commonly
called Carpet Beetles, they feed upon most any dried animal remains. This
would include woolen materials, skins, and feathers. Be vigilant. They're near
impossible to avoid totally, but can be handled if you keep an eye out for the signs.
 
Ken Zentzis
Wichita, Kansas