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.
From the dining hall at Las Cruces, pasture, a road, and some small towers, possibly for cell service, are visible on the ridge at the western side of the forested reserve. The ridge is accessible with about an hour and a half hike down to Rio Java and back up the other side.
Here are a couple of views from the ridge, which were surprisingly clear. In the past, I’ve never seen the station or Talamanca Mountain range (where Las Alturas lies) so clearly.
I’ve never seen this before: a few hundred riffle beetles, Elmidae, all gathered behind a boulder in Rio Java. The larva are common, and I’d rarely see individual adults—here, in the thin film of water cascading over the boulder, were hundreds.
I don’t know what this fly is or does, and it’s maggot must be phenomenally large (flies, like many other insects with complete or holometabolous metamorphosis, don’t “grow” as adult—little flies aren’t babies, they’re likely just different species). On top of it’s size, there were pseudoscorpians hitching a ride on its legs (phoretic dispersal), so when it landed on our current, they began to climb down and investigate their surroundings!
I’ve seen some phoretically dispersed mites on dung beetles (an Instagram post I can’t link) and tabanid flies before too.
A few years ago, a NAPIRE student of mine, Jerry, investigated predation risk of crabs in and away from leaf litter. He found substantial predation in the assay, and, this year, Zane is picking up the idea again (more to come).
The crabs are fairly abundant in the streams, but their densities can vary greatly, and, overall, the density is lower in the larger reaches of Rio Java (greater discharge) and those crabs that we do find in the river have a larger carapace width—big crabs in the big river. Perhaps predation is driving this pattern! And look, here’s a pile of dead crabs, partially eaten, probably by a mammal adjacent to a small backwater pool within the river.