I think these smaller one are Neivamyrmex—it’s not possible to see their tarsi, which is a critical characteristic in determining genus, but they are certainly smaller and less conspicuous than others I’ve seen. These were moving along a log over Quebrada Culvert.
I’ve observed other Eciton in La Selva and Palo Verde, and these could also be Eciton from the Wilson Botanical Garden.
There are all kinds of cool things about this Chrysomelidae tortoise beetle (Hemisphaerota cyanaea) on the internet, including:
Their capacity to stick to leaves. These bizarre little, herbivorous beetles stick themselves to Saw Palmetto leaves with the help of thousands of setae (hairs) soaked in excreted oil when disturbed by a potential predator.
And look closely… there are POLLEN grains all over the little beetles. Can you imagine having hundreds of sticky bouncy-ball-size pollen grains attached to your body and eyes!? The micro-world of biology is fascinating.