Cuckoo Spit

This is the nymph stage of an insect known as a froghopper which produce this cover of frothed-up plant sap resembling spit. The nymphs are known as spittlebugs and the froth as cuckoo spit.
The froth serves a number of purposes. It hides the nymph from the view of predators and parasites, it insulates against heat and cold, thus providing thermal control and also moisture control. Without the froth the insect would quickly dry up.