I've been discussing this recently with other county moth recorders, and the situation is a bit confusing. There are three taxa involved, as per Steve's notes above:
- 'true' Prays fraxinella
- melanic form of Prays fraxinella (white head, some trace of wing markings), that has been called by some, but apparently not all, "form rustica"
- Prays ruficeps, which has dark wings and a yellowish head, with no trace of wing markings. Some, but not all, sources have referred to this as synonymous with the taxon "rustica".

So this needs treating with care, especially the "rustica" name. I agree that we need a new species "Prays ruficeps", and that an aggregate for "Prays fraxinella/ruficeps" would be useful, but we're left with the taxon "Prays fraxinella form rustica Haworth, 1828", currently in the NHM inventory (TVK NBNSYS0100004854). I suspect that some of the specimens recorded as "Prays fraxinella form rustica" are actually melanic P. fraxinella, and others will be P. ruficeps.

My suggestion would be that the current "Prays fraxinella form rustica Haworth, 1828" is changed to "not recommended", and links to "Prays fraxinella/ruficeps" as its recommended name.

But I agree with Steve that *all* older records of Prays fraxinella probably need to be treated as "Prays fraxinella/ruficeps" unless there is photographic or specimen evidence to check.