Excerpt: Representatives of the family Cercopidae are commonly known as "spittlebugs" because the nymphs cover themselves with saliva-like frothy masses composed of bubbles of air trapped by motions of the abdomen in fluids discharged from the alimentary canal. Spittle protects nymphs from desiccation, but they are able to abandon it for brief periods while migrating to new feeding sites or to other host plants where new masses are produced. Gas exchange by nymphs immersed in spittle is accomplished through spiraculae situated in a protective chamber formed on the ventral side of the abdomen by extended tergites.
"An Annotated List of the Spittlebugs of Michigan (Homoptera: Cercopidae),"
The Great Lakes Entomologist: Vol. 3
, Article 1.
Available at: http://scholar.valpo.edu/tgle/vol3/iss1/1