Suds?

I have some lemon balm, mint, stinging nettle and a couple other plants that seem to have little suds on them. It only seems to be on the lower leaves, but it doesn't seem to be doing anything.

Does anyone know what this might be? Or if it might end up being destructive?

Does it look like these:

http://organicgardensite.com/bugs-harmful/spit-bugs/


When I was a kid, we called them spit bugs. We usually only saw them on weeds and wild plants, so I didn't really pay much attention to potential damage, but the above website does say they can deform plants.

I've never seen the actual bug, but yes, that's what the suds look like.

What can I use to make them go away? What will eat them?

What do I have a deficiency in? Lizards? Frogs?

They're not usually especially harmful, apparently, and can be removed by spraying with a hose.