I think the first one is a fly - anything with a dual frass trail usually is.I'm afraid I also think the second one is a sawfly (sawfly mines are very common on alders in Cardiff at this time of year).Sorry can't help with the Phyllonorycter - with around 4 species on alder I think these need breeding through to be sure.
Thanks George, it looks like I have quite a bit to learn here! I've now got the pupae, the caterpillar and the undetermined leafmine in jam jars so we'll see what happens!
Best to start with trees other than alder, oak, willow and hawthorn, all of which can be tricky. I never even look at mines on oak as most are impossible without rearing through.Hazel and sycamore are good starters - relatively few species and most are lepidopterous.
1 yes, Dipterous most likely Agromyza alnivora2 F. dohrnii - many of the blotches becoming elongate and not round and also time of year a factorDave
Thanks Dave - would it be safe to record is as A alnivora? There seem to be few previous county records for it as far as I can tell.