This is a group that seems almost certain to be more complicated and speciose than is currently understood. Blackman and Eastop note that there are two species that are likely not truly congeneric. I agree that C. maxsoni and C. incognita are likely not closely related, but I think there are at least two species lumped within C. incognita. In fact, following my winter 2018 collection curation work, I am now hypothesizing four species currently confused under the name C. incognita. All of them are found on the foliage of Symphoricarpos in the spring, living among slightly curled leaves, and tended by ants. I am working hard this season to re-collect as many of these as possible on Symphoricarpos that are identified to species — it is likely that each of the four species actually specializes on one species of Symphoricarpos.
The fundatrices of the Cedoaphis species on Symphoricarpos are highly specialized and have been confused with Aphthargelia in the past, probably due to uncertainty as to what each genus would look like in the fundatrix stage. Further, the dogma put forward in Blackman and Eastop and elsewhere that the fundatrix lives on the roots in C. incognita is obviously not the case for the Cedoaphis I get on Symphoricarpos. This is yet another example of a situation where concerted study of my own samples might lead to an interesting paper, if only I (or perhaps you?) put the time into it.