A nest of leaf-mimic katydids! They are about 3 to 6 cm (1.5 to 2.5 inches) long and look like leaves. I think these are Pterophylla camellifolia, or "true katydids" (common true katydid). Apparently there are over 1,000 species of true katydids (only about 4 in North America). They can produce a variety of sounds, some of them incredibly loud. I saw and heard them during the entire hike, but only saw one large gathering like this.
