For over 100 years, the lovely little micro moth Lyonetia prunifoliella was thought to be extinct in the UK until it was rediscovered in the 2000s in southern England. It took a while to spread across the country but was found new to Wales, near Holyhead, last autumn and, soon afterwards, found here in south Wales, at Kenfig National Nature Reserve, though just one larval mine was found despite much searching by Butterfly Conservation’s senior moth ecologist George Tordoff.

This year, though, George says, it’s really taken off in south Wales: he’s found it in various Cardiff parks and at Lavernock Nature Reserve. When I heard this news last Sunday, 1 October, I immediately decided to go searching, focussing in particular on the suckering growth of Blackthorn (Prunus spinosa), the tree this moth appears to favour locally for its larval leafmines (though it is known to use other roseaceous trees elsewhere).

Last Monday I found Lyonetia prunifoliella mines immediately at the first place I looked, and have since found it at six locations in my surrounding area, sometimes in abundance, other times just one or two mines, despite a plentiful supply of young Blackthorn leaves. The mines are relatively easy to identify, as the larvae eject their frass from the mines in a ‘string of black pearls’, a rather poetic description from someone on Twitter but easy to remember. (The photographs above show the upper and under sides of the same leaf, with the larva apparent above and its frass ejected below.)

Although most mines I’ve seen have been empty (this moth overwinters as an adult), a few have held larvae, and I was particularly delighted last Thursday to find a group of five cocoons, strung like hammocks on the underside of leaves with silk produced by the larvae before they pupate. I’ve yet to see an adult moth but will definitely share that exciting moment when it happens.