Not all the diversity of a forest is easy to see. Today I want to show you some of the smaller and more elusive creatures we’ve found over the last few weeks in El Yunque.

First, here’s one of the forest’s more common but hard-to-see species. This is the coquí frog, Eleutherodactylus coqui. Its loud call fills the forest from late afternoon to dawn, but the frog itself is cryptic. We were walking past one of our transect lines, marked with these painted PVC poles, and happened to look down. This frog was looking back at us – it had made a home in some water pooled in the tube!

Here’s another species which is very common but well-hidden because of its coloration. The snail, Caracolus caracolla, is often foun on the forest floor and in the trees. We often found it engaged in copulation with other snails (no photos here!) but only once when laying eggs. Here you can see one nestled in a tree branch with several large eggs beside it. I was amazed to see how many, and how large, were the eggs a single individual could produce.

Next, a rare moth, but a highly-visible one. This is Cosmosoma auge, an arctiid species. The bright coloration is an aposematic warning indicating its body is toxic for many species to eat. We found this resting on the wall of a field station dormitory.

And here is a discovery from a Ficus sp. tree. We cut a branch out of the canopy using pruning poles, carried the branch a few kilometers back to our lab, and found what appeared to be another branch attached to the first. Turns out it was a very well camouflaged caterpillar hanging on to the branch! It is Pachylia ficus (the fig sphinx moth), which specializes on eating fig species. Figs are a difficult genus to eat – they produce abundant sticky white latex in the stems and leaves, deterring most herbivores (but not this one). It had a wonderfully soft and smooth body that pulsated as it walked. I took a video, showing its activity.

And finally, my favorite, another leaf hitch-hiker. We found this on a leaf of Cecropia schreberiana. It is Gaeotis flavolineata, an arboreal semi-slug – a species evolutionarily somewhere between the snail and the slug. It has a beautiful green shell that doesn’t completely enclose its body. We found many of these last year, but very few this year, for whatever reason. This one snuck off of its host plant and went for an adventure in our lab. I was also able to take a video of it traversing a leaf – I love how its posterior moves as it negotiates the contours of the terrain.

I think it takes a long time to fully appreciate the diversity in an area like this. We’ve been here for only five weeks over the course of two years and are still finding new things. The next time you drive past a forest, or go for a short walk, think of everything else that still remains hidden!