Larose Forest. From spring through fall these little balls of 'spit' are familiar sights on plants everywhere. They are made by spittlebugs (Cercopidae). Or more correctly, by spittlebug nymphs who create this protective case around themselves. If you gently push away some of the spittle you will see a bright green nymph inside. They create this case by emitting a secretion from their behinds.

Here you can just see part of the nymph in the midst of the spittle.