I uncovered the soft-bodied, green nymphs this morning by gently spraying the spit with water. Three were hiding in a quite large spit, head down, nestled in the joint between leafs and stalks, so that they resemble plant buds. In the afternoon they were covered again in the spit. To make the spit they mix air with their watery deyections and a surfactant secreted by abdominal glands using their legs, and they rest head-down, the spit rapidly covers them.
The adult - said to rememble a frog - is found from June all through the summer and until the first frosts. It has powerful rear legs and is able to jump long distances - hence the 'froghopper' name and it is is found in the same places as the larva. The following photos, from July 2007 illustrate the large colour variation of the adults, with have similar feeding habits as their sessile nymphs, but with a very different, much more active lifestyle.
A review of Philaenus spumarius life history indicated that there is no less than 16 colour forms, and a lot of research has been devoted to the genetic basis of this colour polymorphism.
Yurtsever, Selcuk (2000). On the Polymorphic Meadow Spittlebug, Philaenus spumarius (L.) (Homoptera: Cercopidae). Turkish Journal of Zoology, 24 (24), 447-459. here.