dulosis vs helotism

dulosis

noun
  • process by which parasitic ants steal pupae from the nests of other ants and raise them in their own nest, so that they become part of the colony and perform tasks in it. 

helotism

noun
  • A form of mutualism in which one species is forced to perform tasks for another, for their mutual benefit 

  • The permanent oppression of a nominally free group of people 

How often have the words dulosis and helotism occurred in a corpus of books? (source: Google Ngram Viewer )