Spittle Bug (Philaenus spumarius)
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Suborder: Auchenorrhyncha
Infraorder: Cicadomorpha
Superfamily: Cercopoidea
Family: Aphrophoridae
Genus: Philaenus
Species: Philaenus spumarius
Common name: Meadow Spittlebug, Froghoppers
There are about 2400 species of spittlebugs or froghoppers world wide and about 15 in New Zealand
The only one that is not a native is the Meadow Spittle Bug ( Philaenus spumarius).
These insects are best known for their nymph stage, which produces a cover of frothed-up plant sap resembling spit. The nymphs are therefore commonly known as spittlebugs, or spit bugs, and their froth as cuckoo spit, frog spit or snake spit.
The frothy bubbles (sometimes call cuckoo spit ) is the intriguing thing about this insect. The nymph produces this protective covering in a most remarkable manner by forcing a combination of fluid from the anus and a gluey gland excretion out under pressure, as from a bellows, to make uniform bubbles. The tail pumps up and down to operate the bellows and keep the bubbles coming one every second, and the nymph is soon hidden under a mound of white foam, protected from the sun and from insect predators. The insect can only breath by taking air from one of the larger bubbles or from air at the surface of the foam. The froth also insulates against heat and cold, thus providing thermal control and also moisture control. Without the froth the bug would quickly dry up.
The nymphs pierce plants and suck sap causing damage, and much of the excess filtered fluids go into the production of the froth, which has an acrid taste, deterring predators. In New Zealand they are not serious pests.
Adult froghoppers (Spittlebugs ) can fly or jump from plant to plant; some species can jump up to 70 cm vertically: a more impressive performance relative to body weight than fleas. The Spittlebugs adults can accelerate at 4000 m/s2 over 2mm as they jump up to 100 times their length.
Spittle foam on a nodding thistle with nymph inside 
The nymph coming out of its foam protection.
Spittlebug nymph
How a spittle bug nymph exudes excess moisture by extending its abdomen and then contacts it forcing out the liquid. 
An adult Meadow Spittlebug on watercress
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