Cuckoo spit...

Cuckoo spit is a white frothy liquid secreted by the nymphs of a sap-sucking insect known as a froghopper.

This froth has no connection with cuckoos.

It is secreted by the immature stages of sap-sucking insects known as froghoppers, presumably as a means of protecting themselves against predators.

The adult insects are present during mid-late summer and live openly on plants. They do not produce cuckoo spit or cause any noticeable damage.