With an unusual amount of time in the garden of late (spring 2020), due to the covid-19 global crisis, we've spotted things we might have passed by in haste otherwise. This is happening throughout the garden, like when we realised we have multiple different species of bees . . . rather than just "Honey" & "Bumble", we've discovered all sorts of others from "carpenter", to "Leaf-cutter", to "Hover".
At first I thought this thing here was a spit of foam, or sap, or even a bird poop on a recently planted young tree in our garden. However, on closer inspection it proved to be the cunningly disguised Pusmoth. I like the Latin name too, Cerura vinula.
The caterpillar can squirt fomic acid at potential attackers if threathened! They cocoon and over winter from September
to early spring and fly from May until July, a much longer life span that I had thought Moths typically enjoyed...