“These forms are often accidentally elevated to subspecies status when they appear in literature. Not adding the ‘f.’ (form) or morpha implies that the taxon is

“These forms are often accidentally elevated to subspecies status when they appear in literature. Not adding the ‘f.’ (form) or morpha implies that the taxon is a subspecies instead of a form, as in Biston betularia carbonaria instead of Biston betularia f. carbonaria. Rarely forms have been elevated to species status as in Biston carbonaria. Either of these two circumstances might lead to the erroneous belief that speciation was involved in the observed evolution of the peppered moth. This is not the case; individuals of each morph interbreed and produce fertile offspring with individuals of all other morphs; hence there is only one peppered moth species.” - https://en.m.wikipedia.org/wiki/Peppered_moth https://en.m.wikipedia.org/wiki/Peppered_moth