Under a log around the Las Alturas field station, Cristian found this predatory, land planarian. These flatworms are predators of other invertebrates, including snails and slugs, and kill their prey, more-or-less, by vomiting digestive juices onto them… then sucking up the slurry. That said, they are harmless to humans as free-living organisms, unlike many other species in the animal phylum Platyhelminthes, which are parasitic.
I’m aware of one important invasive land planarian, and had seen some in Palo Verde, but there appears to be very little information concerning land planarians of Costa Rica. Indeed, a Google Scholar search produced a couple of papers, most of which were written before 1970.
Another individual found at Las Cruces on the tourist cabins: