‘Cuckoo spit’ or ‘Cuckoo grog’ as me Dad would say.
The frothy mass of white bubbles found on plants from early May ish … looks like spit .. and appears about the time that Cuckoos arrive back here. Hence the name.
Inside each ‘spit’ is a juvenile (harmless) Froghopper insect aka a ‘Spittle Bug’.
Did anyone else grow up thinking Cuckoos must have done an awful lot of spitting ….. ?