The reason for our trip
Before I start in on this chronicle of adventures, introspection and caterpillar facts, let me explain exactly what I was doing in Costa Rica this New Years, and why I was there at all. It all started in November of 2017, when I was applying to grad school. That month, a paper came out in Germany documenting plummeting insect populations. Since 1980, the paper reported, the amount of insect biomass collected in traps on protected areas fell by nearly 80 percent.
This news freaked me out. If such drastic declines were evident in German insect populations, where else where they happening? News articles cited plenty of anecdotal evidence for declines in the US, most notably people who remembered scraping bugs off their windshields in the 80s, compared with today. Through the haze of childhood, I could recall similar comparisons. When I was five or six I remember my family pulling into gas station parking lots full of drifts of dead insects, stopping under porch lights aswarm with moths, listening to clumsy june bugs bumping into window screens in the night.
Over the succeeding months, more papers came out documenting insect declines in different areas. And after I chose a school and moved up to Boston, it was still a hot topic. People were digging up old biodiversity surveys and re-conducting them years later. Those with long-term datasets were hurrying to analyze them. So when it came time to pitch my thesis, I proposed a feature article on insect declines, and went out looking for scientists to profile as an introduction to the topic.
I found these Costa Rica researchers by chance. Lee Dyer, a professor at the University of Nevada, Reno, and his graduate student Danielle Salcido study multitrophic interactions in the tropics, which can get pretty crazy, believe me. Caterpillars eat plants, and wasps parasitize caterpillars. Every now and then, another kind of wasp will come along and use its whisper-twitch front legs to feel up and down the length of a caterpillar to see if it already has wasp larvae inside, in which case it will lay its eggs inside the wasp larvae inside the caterpillar. And those are just a few of the interactions scientists have observed.
The researchers have been compiling a long-term dataset of interactions for nearly 30 years, and are in the process of analyzing it for publication on insect declines (or the lack thereof) at different sites. They’ve collected around 4,500 species of caterpillar in that time (just over half of the estimated number of species in La Selva Biological Station, where they conduct some of their research), and raised them to see whether or not they have been parasitized. This data can provide insight into populations of both wasps and caterpillars, and the complexity of the interactions lends it a dimension that is absent in many straight biomass surveys.
No surprisingly, many of the interactions between caterpillars and parasitoid wasps — and other rainforest creatures — are still unstudied. There’s a lot we don’t know about these delicate connections; a lot we may never know. Dyer said something in one of his talks that stuck with me: “When we lose these interactions, we aren’t only burning down libraries of books,” he said. “We are burning books that have never been read before.”
On the road to La Selva
Our bus to La Selva left at 8 the next morning, and took a winding route through Braulio Carrillo National Park. As we got farther away from San Jose, the hills on either side of us got steeper, but stayed covered in dense tropical forest. Huge, round-leafed plants clung to the steep slopes on either side of us, and several times a sprinkle of rain splattered the windshield of the bus out of nowhere.
We pulled in to the biological station just before lunch, and walked across a shaky plank bridge to the lodgings. Our cabina was a two-story green and brown building with four units. None of the other rooms were occupied. When we stepped out on the front porch, though, we realized that we were sharing the house with five other guests — bats!
Over the next few days we met more and more of the long-term residents; fat, thick-fingered geckos that wiggled up and down the walls looking for juicy insects, juicy insects that were big enough that not even the boldest gecko would go for them — one katydid was about the length of my palm — and huge, heavily-armored millipedes who looked like their segments were protected by angular plates of bone-china.
Outside, we encountered even larger locals; for example, a whole herd of peccaries that roamed the lawns. They didn’t care much about people, but at one point I got too close to one and it turned around and made a noise that sounded like a cross between a snort and a sneeze; I backed off after that. Right next to our cabin, a family of huge greyish birds called guans strutted about emitting low croaking cries.
It didn’t take long for the forest to work its strange magic on me. Every time I stay somewhere like La Selva — somewhere deep in the woods, with minimal accommodations and few people — the same thing happens. I can feel my sense of self slowly washing away in the humidity. Not in a bad way, but in the sort of way that makes me stop looking in mirrors. Like it doesn’t matter what I look like — it barely even matters who I am. As long as I am here, surrounded by this dense tangle of life, I am part of something more important and intricate, woven in like a strand of a straw basket.
The opposite happens in cities, sometimes. I become painfully self-aware, worried about what I look like, what I do, how I present myself. It’s strange, because the anonymity of the cities I’ve lived in means that I’m much less noticeable there than in close quarters with a bunch of researchers. But something about the separation in urban areas — the people stacked on top of each other in tiny box apartments and the faces of all the different people I pass on the street — makes me feel too much like an individual unit.
Anyway, on our first half-day at La Selva, Lee and Dani led the whole group of us on a small collecting walk, looking for any sort of caterpillar we could find. I found a sort of gross one, all rolled up in a leaf that it had tied together with silk. The caterpillar itself was maggot-like, pale and squirmy, and its home was messy, all sticky silk and caterpillar poop. Caterpillar poop is called frass. For some reason that is an easy thing for me to remember, but if you ever forget you can just remember that “frass is from the ass” — LOL.
Walking with the group was a lovely experience in itself, because everyone was so excited about every little thing we saw. The team was a mixed group of older people who had signed up and paid for the trip through Earthwatch. There was a retired Rice professor who’d read just about every environmental book I’d ever heard of, an accomplished bird photographer who chatted with Cano about cameras (she had the same one Cano had just bought), and an excited Argentinian natural educator who exclaimed so loudly over every insect and amphibian we saw. One woman had flown in from England, and two others from the central U.S. There was also one man who used to study spiders and had a joke for every occasion; overall, a very interesting combination of people!
New Years in the rainforest
Our first half-day was New Years Eve, and of course, Cano and I came prepared with pre-purchased champagne and a tiny bottle of vodka. So did the rest of the crew, and we had an impromptu party at the project director and his wife’s cabin. Cano and I spent a good thirty minutes talking to Lee, the project director, and his wife Angela.
“Are you going to be awake at midnight?” Lee asked us.
Cano shrugged, but I said that I was, because I had an article due the next day at noon.
“Then you should go out on the bridge,” he said. “It’s a nice place to be for the new year.”
So that is how Cano and I came to spend the first moments of 2019 standing out on a swaying plank bridge over a tropical river, looking into a tree filled with huge orange iguanas. In the distance we could hear a group of people counting down the seconds until midnight mingling with the hums and screeches of insects.
Caterpillar hunting commences
The next day we got started in earnest. In the morning, we ate breakfast and met the group at the ambient lab — so called because it was an open-air building, constantly taking on the temperature of the outside — and Dani sorted out who would be walking where that morning, and who would be staying back to photograph the few caterpillars we had collected the previous day.
Cano and I had missed the memo on the sort of boots we would need to bring. Hiking boots, it turned out, were not adequate protection from some of the more dangerous creatures we might encounter in the forest, such as the highly venomous fer-de-lance. The project director and his wife were kind enough to lend us their “jungle boots,” which turned out to be high rubber rain boots.
Once we were properly booted and equipped with lots of plastic caterpillar bags, we set off down a narrow concrete track into the rainforest. Everywhere I looked, there was something new and fascinating that caught my attention. Huge dusky moths, poisonous frogs, strangely-shaped orchids, and mysterious natural traces I had never seen before pulled my gaze in all directions. On the ground, parades of leafcutter ants carried little pink flowers into their hole, which could have easily fit a small child. At one point I found a strand of tiny mud wasp nests hanging one on top of another on a delicate thread. My constant fascination with these little natural distractions, though, made me a spectacularly bad caterpillar hunter. At the end of our first walk, I had only found one. One of the other women had at least six caterpillar bags hanging from her belt.
There are several kinds of caterpillar that you are likely to find in January on the paths through La Selva. Some are free-roaming caterpillars that might appear at any point on top or underneath a leaf. And then there are the shelter-builders, like Quadrus cerialis. These are pale, translucent, worm-like caterpillars that create little homes for themselves like they are tucking themselves into bed. They cut into a leaf (their favorite host plant being the leather-leafed understory plant Piper reticulatum), and then stand up on their sticky pro-legs and begin waving their front ends back and forth, producing a thin string of silk as they go. They attach this silk to the edge of the leaf, and again at the center, pulling the edge over them in a little taco-shaped shelter.
This is all very endearing, but then they start to eat, and that’s even cuter, if you can believe that. It is in Quadrus’ best interest to not destroy the integrity of their tiny leaf home. So instead of eating huge holes in the leaves like some species, the caterpillars chew smile-shaped chunks out of the leaf, creating a pattern like a hundred crescent moons scattered on its surface.
On one hike, we were all given a specific host plant to search. Mine was the brown-stemmed, long-leafed understory tree Anaxagorea crassipetala. The trees were fairly small, but we could tell they had been there a long time by the build-up of moss and tiny epiphytic plants that carpeted their leaves. There were specific caterpillars that loved this tree, Lee said. Cano and I did find two caterpillars — a capricious red and black one that danced around on the top of the leaf like a tiny wild horse, and a pale one that hung calmly from an invisible strand of silk like a trapeze artist minus the trapeze — but neither of them actually ate Anaxagorea. They were just wanderers. We collected them anyway.
When anyone found a caterpillar, someone would produce a large clear plastic bag, into which we would stick the insect, as well as a few leaves of its host plant, and tie off the top. On the outside of the bag we would write as much as we knew about the type of plant, the type of caterpillar, and the exact location at which we had found it.
The following couple of days fell into an easy routine. Breakfast was served at 6:30, and then we’d meet at the ambient lab where, Dani, Lee and Angela would delegate tasks. Most of the group would go out and walk the paths on the hunt for caterpillars. Two would stay back and photograph the caterpillars we had already collected. We would meet back at the comedor for lunch at 11:30, and then break until 1. At 1, we’d start over again, some going out walking, some staying behind to care for the caterpillars. At 4 we’d break, and then reconvene at the comedor for dinner, followed by a scientific talk of some kind. Lee gave two — one on the research he’s conducting using his long-term dataset, and another on caterpillar classification.
The only other talk I saw was by Ron Coleman, a researcher at Sacramento State who studies cichlid fishes. He talked about adventures on the bottom of tropical rivers, observing the various parenting styles of fish. Only about half his talk was on the fishes themselves though, and the rest was entertaining anecdotes about Costa Rica, and things you might encounter on the roads or in the forest or even in the towns.
For the rest of the time we were there, I would pay special attention to the muddy river where he and his graduate students snorkeled. I saw lots of fish, as well as a small crocodile, and hoped the researchers were aware of this scaly resident.
During our three days in La Selva, we ate pretty much exclusively rice and beans. Breakfast would be rice, beans, and some sort of egg dish. Lunch: rice, beans and a salad bar. Dinner was rice, beans, and a vegetable or meat dish, along with leftovers from lunch and a small dessert.
On our last day, the man at the desk called us a taxi for that night. Our flight left at 2 a.m. (recall my trip-planning cruelty) and so we needed to be on our way to San Jose by 9:30. The taxi would cost around $150 in cash, but we didn’t have that much, and ATMs close early in Costa Rica. So with the $20 or so we did have, Cano and I took a taxi into the town of Puerto Villejo de Sarapiqui to get more cash for the other taxi. It was all very silly, but I was glad to go to town. It was a tiny town, only a few blocks long. The main strip was bustling with activity. I made eye contact with a dirty-looking dog, and then he attached himself to us like we were old friends. He followed us around for a few minutes until he got distracted by the smell of a fried chicken stand.
We came home afterwards and ate dinner (more rice and beans, of course) and then Julie led us on a night hike through the forest. She and Linda had brought UV flashlights, which didn’t shed much more than a purplish glow on most of the forest, but lit up all sorts of tiny life forms we would not otherwise have seen. It was interesting too, because it seemed like the closer you looked at an object — say, the mossy trunk of a tree — the more details appeared to glow. Several times Cano caught up to me with my nose almost pressed against a clump of lichen or some strange fungus just trying to get a closer look.
If I used the black light flashlight for too long, a sense of unreality would descend, and I’d have to pull out my white light beam to make sure that leaves were still green and the rest of the world was still there. Strange, fractal-forming selaginella looked even stranger in the black light; its kelly-green fronds glowed hot pink under the flashlight’s beam. If I shone it at the ground, bright spots emerged like confetti. Some were flower petals, others bits of leaves or mysterious chunks of lichen or fungus or something else unidentifiable.
Once we got out to the swamp, we found a green tree frog clinging to the top of a leaf, and a twisting colorful snake that disappeared into a tree. Soft rain started falling halfway through. If I turned my flashlight off and looked up, I could still see all the stars perfectly.
On the way back, Julie spotted a fat silvery caterpillar clinging to a blade of grass out in the swamp, tantalizingly out of reach. I decided to volunteer to collect it, so I swung myself off the railing and into the neck-high grass of the swamp. The caterpillar sat calmly as I brought the bag closer and closer, until finally I was able to break off the blade of grass and catch the creature softly in the bag.
It was our last caterpillar of the trip. That night, Cano and I showered for the last time in our little cabina, stuffed all our belongings into our respective suitcases, and caught our flight back to Texas.