Or, to hop abruptly to a different metaphor: there is only one species of butterfly, and it is closely related to the chameleon - probably in the same genus. But there are many different species of fox within the vulpes genus. Here are three encountered in my reading today, from just one text:
Vulpes astuta carnivora, or the Sly Devouring Fox, is a subtle threat in that he rarely shows his true self, but desires only to soothe his prey with an innocuous face before bolting it down. If thwarted, may resort to sarcasm:
Vulpes astuta arguta, or the Clever-tongued Fox, belongs to the same sub-species as the last, but is better known for his smooth tongue and his ability to convince his victim to act in a way detrimental to their own interests. He may then take advantage of the deception to devour his prey, as does V. a. carnivora, or he may seek to deprive them of some other benefit or possession:
Vulpes lasciva dissumulata, also known as the Lusty Brush-tail. A rarer species, of which only the females are seen. Definitely not to be trusted, and motivated primarily by lust for sensual pleasure. These conceal their evil nature not with their words, but with an exceptionally large and luxuriously furred tail. If the tail is pried aside, however, their filthy, stinking underbelly and privy parts may be discerned:
It seems that I'll have to keep an eye out for more foxes in order to flesh out the species tree! Reynard in Sir Gawain and the Green Knight, of course, borrows from all these traditions, including the coward, the vermin-in-the-hunting-field and the (literally!) uncovered deceiver, of which we have no representative today. But sadly, he is too much of a hybrid to be properly classified.
 It's not mixing if the first one never recurs! Juxtaposed metaphors?
 The mirroure of the worlde: a Middle English translation of Le miroir du monde, ed. Robert R. Raymo et al. for the Bodlein Library, Medieval Academy Books 106 (Toronto: University of Toronto Press, 2003). It's very similar to The Book of Vices and Virtues - enough so that either the French source of one must have been copying the other, or they were both indebted to one common source. Mirroure, however, lacks the butterfly metaphor.
 Apparently the author had never visited Australia.
 Inverted commas inserted by yours truly, to make the direct speech easier to decipher for anyone less familiar with Middle English.