Ken has sent me a photo of his spittle bug... it literally looks like spit on your plant. Like aphids, this is a true bug and has the ability to feed directly from plant- sucking (or rather imbibing) plant sap. But first it secretes this "juice" that looks like spit and hides inside the spit while it feeds. This bug doesn't really do a lot of damage but like other plant feeding bugs may spread virus to plants it feeds on.
Simply hose it off plants as you see it. No big deal.