"Describe, with examples, the ways in which Transforming Spells must be adapted when performing Cross-Species Switches"
-- Homework question on Professor McGonagall's blackboard (GF22)
Classification of Transfiguration magic in which one type of creature is Transfigured into another.
References from the canon
- The fourth years had to write an essay about using these after practicing transfiguring guinea fowl into guinea pigs (GF22).
- Apparently it's easier to do the spell when the creatures have similar names (e.g. guinea fowl into guinea pigs), similar appearance (e.g. hedgehogs into pincushions), or both (e.g. beetles into buttons).