Here is my take on imperfect mimicry. I wonder if there are such a thing as imperfect mimicry.
If you take evolution into a count then the specie might just give the illusion that they are a closely related to the dangerous specie.
An example would be a bird coming to a different island where the wasps look a bit different in terms of size, shape or more. The wasps would probably keep some similarity which would not cost so much in terms of performance, like the color of a car.
So, perfect mimicry is not necessary. The specie just has to fool the predator that it is related.
I think it should be called kinship mimicry, not imperfect.
// Per Lindholm may 2014