These tiny tubular things with spines are the nymph (juvenile!) stage of the treehopper, an intriguing little bug that can be found from late spring. Ants carefully tend both adults and nymphs and protect them against predators. They do this because the adults secrete a sweet honeydew mixture that the ants love. Ants do the same thing with aphids for the same reason. This benefits both the bugs and the ants, as you can imagine. The bugs are protected and the ants get a sweet food. It is called a symbiotic relationship.