cuckoo spit

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A frothy mass of liquid secreted on plant stems as a protective covering by nymphs of the spittlebug. Also called frog spit.

Century Dictionary and Cyclopedia

1. n. A froth or spume secreted by sundry homopterous insects, as the common frog-hopper, Aphrophora or Ptyclus spumarius. Also called froth-spit.
2. n. An insect which secretes a froth or spume, as a frog-hopper: called in full cuckoo-spit froghopper.

Wiktionary

1. n. A frothy mass of white liquid that is secreted onto plants by froghopper larvae and serves as a protective covering.

GNU Webster's 1913

1. n. (Zoöl.) A small hemipterous insect, the larva of which, living on grass and the leaves of plants, exudes this secretion. The insects belong to Aphrophora, Helochara, and allied genera.