Muryans ia a race of fairies that dwelt in Cornwall and whose size is slowly diminishing (supposedly for some crime commited centuries ago).
Description
Muryans were once the size of humans. There size slowly dwindled over the years until eventually they were the size of ants (muryons means "ants"). It was thus unlucky to destroy an ant hill, lest it be muryans and they be offended. Now, however, it is thought that they have perished.
Sources
Robert Hunt. Popular Romances of the West of England.