Sawfly mines in elms

Today was too rainy to find adult sawflies, but I did take a look at some leaf-mines in local elms in S Norfolk. I've been interested in these for a while, given that some sources say one species is involved - Kaliofenusa (was Fenusa) ulmi, whilst others list two species - K. ulmi and K altenhoferi.

The apparent differences between these two species are (per Liston 1994, Br.J.Ent.Nat.Hist. 7, 15-18):

a) differences in fine detail of the structure of the head, and the terminal antennal segments, of the adult - no good unless I manage to rear some out (v hard with sawflies) or find the adults in flight (v hard with Tribe Fenusini in my experience so far).

b) species of elm, with K. altenhoferi found on Ulmus minor, U procera and possibly hybrid elms; whilst K. ulmi is on Ulmus glabra. OK, but there has been a lot of discussion recently about speciation in elms, with potentially over 60 British species. Perhaps elm specialists can tell me if what was previously called U. glabra (Wych Elm) is sufficiently different to all the others??

c) position of mine, with K. altenhoferi mines apparently starting mostly in leaf-margins, vs. K. ulmi mines starting mostly in the leaf-blade interior (and "even completed mines often do not touch the leaf edge"). There are rather a lot of "mostly" and "often" here, and Liston also notes that parasitoids may cause mines to cease earlier than might otherwise be the case.

I took the following photos today - 11th June 2019. The majority were in small-leaved hedgerows elm suckers in Shotesham at ca TM24829975. The last two images are of a mine from a larger-leaved elm - perhaps a Wych Elm? - in Poringland at about TG26260349.

One could arguably make a case for both species here, but I'm not sure I'm buying it. Many of these mines (apart from the last) were from the same cluster of trees and were surely relating to the same species. Opinions very welcome.

Note - I believe that the form of the mine, larvae and frass rules out other potential leaf-mining species, but please do say if you think they might be something else.

Given the two clusters of frass, I wonder if this might be two mines that have run into one? 

Not reaching the middle so altenohoferi?

Not quite reaching the edge so ulmi?

Not reaching the middle so altenhoferi?

Larger leaf from Poringland, mine nowhere near the middle - so altenhoferi (but if Wych Elm should be ulmi?)

close-up of previous