At this time of year, whenever I spot a Wych elm tree, I spend a bit of time staring at the leaves. I look for two things in particular: the first is to see if I can spot any White-letter hairstreak butterflies flitting around, usually at the top of the tree but also lower down; and the second is to see if anything has been nibbling at the leaves. My searching paid off last week when I spotted the distinctive signs of leaf damage caused by the larvae of the Elm zigzag sawfly (Aproceros leucopoda), not necessarily a good thing as this is an invasive species, which I found new to Wales in October 2021 (Zorro comes to Wales) and which is now slowly spreading westwards. But, more interestingly in this particular case, I found one of the cocoons the larvae pupate in, a very delicate, woven-silk structure (you can see an occupied cocoon on the Forest Research website). This one was empty so I guess that’s one more adult sawfly helping to spread the species further.