Stories
Mystery of the Yellow Bulbs: Discovery in the Amazon of a New Caterpillar-Ant-Parasitic Plant Relationship
“Huh, that’s weird”, I muttered as I trudged through the mud in the rainforest. Even though the sun was setting, it was still hot and steamy, and sweat was dripping into my eyes as I stared at a tree with bizarre yellow outgrowths…I didn’t know that what was in front of my eyes was an ant-caterpillar parasite relationship.
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Some sort of fungus? That was my first thought. After all, I’ve seen tons of strange-looking fungi in the Amazon by now. But something about these yellow bulby-looking things piqued my curiosity, so I walked up to take a closer look.

A tree covered with strange yellow bulbs in the jungle
Inspecting them closer only made things more confusing. They didn’t really look like fungi, at least not like any I had ever seen before. Was it a fruit produced by the tree? Plant lenticels? I started to take some pictures.
A closer look at the mysterious yellow “bulbs”
That’s when I noticed something really interesting. As I scanned the tree’s alien protuberances, my eyes locked onto something I wasn’t quite anticipating: caterpillars! I had definitely never seen or heard of, anything like this before. They appeared to be munching away on the yellow bulbs.

An unknown caterpillar eating one of the yellow bulbs
I quickly noticed there were also ants surrounding these caterpillars. The ants were not attacking the delicate butterfly larvae, so this had to be some sort of symbiotic relationship between the caterpillars and ants. While I had little idea at the time what I was looking at, my background in entomology was telling me one thing: this was something cool.
An ant, Ectatomma tuberculatum, guarding a caterpillar

Always gotta show a finger for scale
By this point, I had returned to the tree with my colleague, wildlife photographer Jeff Cremer. We took several shots of the caterpillars, ants, and yellow bulbs. This kind of mutualistic caterpillar-ant relationship is known as myrmecophily and has interested scientists for a long time. Caterpillars belonging to the family Lycaenidae have a special structure known as the dorsal nectary organ, which secretes sugars and amino acids. This sweet, nutritious reward is what keeps the ants around and in return, the ants protect the caterpillars by driving off hungry predators and parasitoids.
An attendant ant tapping the caterpillar and receiving a nectar droplet.
Filmed thanks to the help of Chris Johns
As I was inspecting this bizarre caterpillar-ant interaction, I noticed something flutter just above my head. A butterfly! Not just any butterfly, I could immediately identify it as lycaenid and it had a distinct yellow spot on its hind wing that looked remarkably like the yellow bulbs. Was this the adult of the caterpillars!?

A butterfly with a yellow wing spot lands on the tree
Ok, Homework Time
I wrapped up my fieldwork and headed back to the states, but I was dying to figure out what was going on here. To recap, we observed:
- Mysterious yellow bulbs growing on a tree
- Caterpillars eating the yellow bulbs
- Ants taking care of the caterpillars
- Butterfly with yellow wing spot lands on the tree with yellow bulbs
I assembled the photos from the trip and started emailing the top butterfly experts as well as botanists. The responses I received were mostly along the lines of “I’ve never seen anything like this before” and “there’s nothing published on the life history of the butterfly”. Ok, so it seemed like we were on to something new here.

With the help of some experts, we were able to identify the butterfly as Terenthina terentia, which belongs to the family Lycaenidae. While this family contains around 6,000 species, the Neotropical lycaenids are still only partially known and poorly studied (Pierce 2002). Many species of lycaenids are known to engage in relationships with ants (aka myrmecophily) so our caterpillars definitely fit these criteria.
Filming this strange caterpillar-ant parasitic plant relationship
Several botanists emailed my pictures around to their colleagues until we were finally able to ID the yellow bulbs as a “very unusual and rarely seen” parasitic plant belonging to the family Apodanthaceae. Ever heard of that? Yeah, me either.
Apodanthaceae is a small family of parasitic plants that live inside other plants and they only become visible once the flowers burst through the bark (Bellot 2014). The species we found is possibly Apodanthes caseariae and there is little known about their ecology, what pollinates them, or how they infect their host plants. Our observations appear to be the first record of an insect utilizing Apodanthes as a host plant. The strange yellow bulbs of this plant appear to emerge once a year around October through January and then fall off.

The yellow bulbs later identified as a rare flowering parasitic plant
In January, my colleague Phil Torres visited this site and checked out the caterpillars. You can see the yellow bulb flowers are more developed at this point.
What’s the Take-Home?
Although this species of butterfly, Terenthina terentia, was described over one hundred years ago, we knew essentially nothing about how it lived its life until now. In other words, we helped to describe its life history by documenting the larval stages, host plant, and ant-associated behavior. By observing and studying this complex relationship, we can gain more insight into the diverse array of biological interactions in the Amazon rainforest.
Compilation shots of a potential Terenthina terentia caterpillar showing its morphology
However, our work is far from over and many questions still remain. Is this the butterfly’s only host plant? How does it know when the parasitic plant is emerging and how does it find the yellow bulbs? What purpose does the butterfly’s yellow wing spot serve?
Perhaps the yellow wing marking helps the butterfly blend in with the yellow parasitic plant and reduces predation by birds. While this hypothesis needs further attention, the similar wing pattern and observed host plant could lend support to the idea of a long-term co-evolutionary relationship between the flowering endoparasitic herb and the Terenthina terentia butterfly. In any case, we’ll attempt to continue to pick apart this fascinating Amazon mystery which will undoubtedly result in even more questions!
By Aaron Pomerantz
Entomologist. Get in touch on Twitter @AaronPomerantz
Special thanks to colleagues in and out of the field who assisted with this project, especially Jeff Cremer, Frank Pichardo, Chris A. Johns, Phil Torres, Christie Wilcox, Jason Goldman, Trevor Caskey, and Alex Gardels. Thanks to Andrew Warren, Alex Wild, Naomi Pierce, Adrian Hoskins, Sidonie Bellot, and Robert Robbins for help with insect/plant identifications and expert input.
References
Bellot S, Renner SS (2014) The systematics of the worldwide endoparasite family Apodanthaceae (Cucerbitales), with a key, a map, and color photos of most species. PhytoKeys 36: 41-57
Pierce NE, Braby MF, Heath A, Lohman DJ, Methew J, Rand DB, Travassos MA (2002) The ecology and evolution of ant association in the Lycaenidae (Lepidoptera). Annual Review of Entomology 47: 733-771
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Fantastic to be deep in the forest surrounded by incredible wildlife with our amazing guide Juan Carlos Yatto, who really knew his stuff! Also his photography skills meant that we could share our experience even better through his telescope using our phone cameras! We learned so much!! He went to extra lengths to find butterflies and moths for us along with so many different birds and monkeys. This was a travel highlight for us as experienced wildlife travellers. We loved our spacious room with no windows and open to more wildlife visitors but after 5 nights the bed could have been a little more comfortable. Luckily we had a second bed to use. Otherwise it was fantastic with hot water showers and fresh drinking water all the time. We were amazed at the variety of food on offer for breakfast, lunch and dinner and couldn’t believe they could have such a wonderful food offering in such a remote location. Even the wine and cocktails were great. I highly recommend spending the extra money and time getting to this location. We stayed at another lodge later which was closer to Puerto Maldonado and there was far less wildlife. Read all
Ederson made the stay at the lodge amazing. I have had many guides around the world and Ederson may be the best I have had across 50 countries. The lodge itself is nice, and has electricity. Food is good, and you really feel immersed in the amazon staying there. Its great that a portion of the money goes back to conservation and research. Noteworthy details: Ederson, the "commander" is the best guide! Read all
Through a travel agency in Lima we booked a 4day/3-night stay at Refugio Amazonas. We were looking for a lodge that was far away from Puerto Maldonado but didn't require almost a day to get there (like TRC), with extensive walking trails and with the principal jungle highlights nearby. We were not disappointed. As we later learned, this is probably the best lodge in the region! Well run, quiet, excellent food, beautifully located in the middle of the forest, everything was "right". Surprisingly there were few mosquitos or bugs. Emperatriz (MP as some call her), our guide, has a keen eye and took us on some unforgettable walks and boat rides, both day and night. The birds at the clay lick were fantastic. The lodge also had evening lectures by young researchers as well as special activities such as collecting night moths and setting a trap camera. We later received videos and photo's of what was found (including a puma!). I can recommend this lodge without reservation. Read all
Abbiamo scelto il Tambopata Research Center perché il nostro obbiettivo era di poter vedere le are da vicino. Ci siamo stati ad inizio dicembre scorso, l'inizio della stagione delle piogge, perciò abbiamo scelto di restare 5 notti/6 giorni, abbiamo messo in conto di perdere delle giornate a causa della pioggia e per la lontananza da Puerto Maldonado, per nostra fortuna durante il nostro soggiorno ha piovuto solo il giorno di partenza proprio quando arrivavamo in aeroporto. Non c'é stato un giorno che non ne abbiamo visto: are di diverse specie e colori e molti altri uccelli e primati, spettacolare l'incontro a pochi centimetri con un formichiere bianco, ma non il giaguaro. Consigliamo di pernottatre almeno 3 notti, il viaggio é molto lungo. Noi eravamo all'aeroporto di Lima già alle 8:00 di mattina e tra un volo in ritardo, uno spostamento in bus di ca. 45 minuti per arrivare al fiume, ed un trasferimento in barca veloce, siamo arrivati al lodge verso le 16:30. All'aeroporto ci ha accolto la nostra guida privata Alfred, che ci ha seguito per tutto il soggiorno, di giorno in giorno abbiamo deciso le escursioni da fare, ed Alfred si é rivelato essere una super guida, un occhio di falco per scoprire anche il più piccolo uccellino, con pazienza é riuscito a farci camminare chilometri nella giungla, ci ha spiegato molto sulla flora e fauna. Bravissimo a far video e foto con i nostri telefoni col suo binocolo e cavalletto che si portava sempre appresso, queste foto sono dei magnifici ricordi. TRC non é un hotel, é un centro di ricerca per le are, in mezzo ad una foresta ed a ore dal primo centro abitato, perciò non avevamo delle grandi aspettative ne sul cibo ne sull'alloggio Read all
This place is a treat!! Incredible flora & fauna, food and service - the staff is quite attentive. Interesting research, with lots of potential. Visiting the Peruvian Amazon Rainforest is a must do! Read all
We had the most amazing time EVER at Refugio Amazonas, and I am so very glad I booked our stay here. Honestly, this is to date probably the best travel experience we have ever had and I will never forget our time in the Amazon here. First of all, the lodge is beautiful. Our room was lovely. The beds were comfy. The bathrooms are large. It is incredible waking up to the sounds of the jungle and falling asleep to the insects at night. We did have some insects in our room, and a rodent, and even a tarantula (non poisonous)! But it was part of the experience. The food was great and they prioritize native and local ingredients. My partner and I are both vegan and they took SUCH good care of us. The food was delicious, and we had ample vegan options every meal. Everything from the first email contacts with Katia to the transfers to the first night info session to the activities-- which I will get to in a second-- was incredible. It is a bit pricey, but everything is included and there is nothing you need to worry about, and it was so worth it. OK now for the best part-- the activities. Holy wow. First of all, we had the best guide EVER-- Juan Carlos. He was amazing. He is a bird expert, knows so much about the animals who live in the rainforest, the insects, the trees, the plant life, it was incredible. He also so clearly cared that everyone in our group had an amazing time. He took so many pictures for us, pointed out so many animals for us, and made sure we all enjoyed every moment. I can’t thank him enough because it made our time here so very special. We went on many activities that were amazing, and we saw so many animals— capybaras, howler monkeys, capuchin monkeys, so many incredible insects, frogs, tarantulas, so many many birds and butterflies. Every activity was amazing but the highlights were the macaw clay lick and the canopy tower. And we were super impressed and happy to hear about their commitment to conservation, protecting the animals, and supporting the native community nearby. There is so much I could say about our stay here but I would recommend a 3 night stay over 2 nights (so you can do more activities), and make sure you read the guides they send via email before you come so you pack correctly and know what to expect and bring--the guide includes everything so that there are no surprises, and we knew exactly what to expect, although our stay exceeded our expectations! I highly, highly recommend staying here, it was magical, it was a once in a life time adventure, and I will never forget it. I also want to shout out the manager of the lodge, I forgot her name, but she was incredible, as well as the service staff at meal times, who were so kind and helpful to point out what was vegan all of the time. I truly hope we can come back some day!! Read all
The lodge was kept very clean, and the staff paid close att to people's needs. It was very easy find activities and the guides were excellent with a genuine intended approach towards sustainability and environment longevity. Read all
A superb stay in a top class Lodge which gave a wonderful insight into the Amazon wildlife. Our guide was Juan Carlos who has incredible knowledge and a lovely sense of humour. The staff in the lodge were so friendly and the meals provided were something to look forward to. A wonderful experience! Read all
I traveled with my mom, who is elderly, and we were a little scared but decided to go for it. Upon arrival, our guide, Christian Herrera, was waiting for us. He was very friendly and had extensive knowledge of the area. The lodge is wonderful, 100% connected to nature. The food is delicious, and everything there is to do near the lodge is incredible. I highly recommend going to the tower at sunset and the macaw clay lick at dawn. Thank you guys for everything, the stay was a dream. Read all
This place totally stole the show! We came to Peru for Machu Picchu, but I think it’s safe to say Refugio Amazonas became the absolute highlight of our trip.It manages to be as luxurious as a stay in the Amazon can be without feeling like too much hand-holding. The rooms don't have windows, which lets you be super close to nature. Sure, that means moths, but it also means drifting off to the peaceful sound of cicadas and waking up to howler monkeys. I honestly can't remember the last time I had such deep, peaceful sleep.The food is another major plus; it's exceptionally fresh, especially considering it’s a buffet. You should absolutely check out their menu, too—it’s one of the most thoughtful and best-designed ones I’ve ever seen. Kevin hosted us at dinner most nights, and he was such great company and so mindful of my wife's dietary restrictions. It really adds to the experience when you feel that people genuinely care.We also took advantage of the exceptional massage here. After a long trip, a massage by Kelly was exactly what the doctor ordered.But the real star of the show is the activities and the guides. We got incredibly lucky with the very best: Juan Carlos. He was funny, great company, and extraordinarily knowledgeable. All the guides at Refugio Amazonas understand that it's not about just ticking a box but about living the experience. That’s why you might take 30 minutes longer to complete a hike—because you decided to spend some time watching Tamarins playing with each other. Jonathan was another guide we had a wonderful, very knowledgeable, and fun time with. We honestly just didn't want to leave and wish we could have stayed longer. Read all
We just finished three weeks in Peru and without a doubt Refugio Amazonas lodge was a real highlight of the trip. You need to know there is NO AC but honestly you don't need it at night in October, There's a ceiling fan and the bed was super comfortable with netting and additional fan within the bed area. The sounds of the jungle at night and Howler monkeys in the morning was great experience. The staff was excellent with a special mention for Paul our guide. He is an excellent Birder as well and can't thank him enough for over 110 new bird species during our four days there. The early morning Macaw clay lick experience with the boat ride in the dark was very cool. The buffet style meals were ok, make sure you bring shoes for mud and extra to walk around with in the lodge. Refugio provides boots for water on trails. See photos Read all
This place totally stole the show! We came to Peru for Machu Picchu, but I think it’s safe to say Refugio Amazonas became the absolute highlight of our trip.It manages to be as luxurious as a stay in the Amazon can be without feeling like too much hand-holding. The rooms don't have windows, which lets you be super close to nature. Sure, that means moths, but it also means drifting off to the peaceful sound of cicadas and waking up to howler monkeys. I honestly can't remember the last time I had such deep, peaceful sleep.The food is another major plus; it's exceptionally fresh, especially considering it’s a buffet. You should absolutely check out their menu, too—it’s one of the most thoughtful and best-designed ones I’ve ever seen. Kevin hosted us at dinner most nights, and he was such great company and so mindful of my wife's dietary restrictions. It really adds to the experience when you feel that people genuinely care.We also took advantage of the exceptional massage here. After a long trip, a massage by Kelly was exactly what the doctor ordered.But the real star of the show is the activities and the guides. We got incredibly lucky with the very best: Juan Carlos. He was funny, great company, and extraordinarily knowledgeable. All the guides at Refugio Amazonas understand that it's not about just ticking a box but about living the experience. That’s why you might take 30 minutes longer to complete a hike—because you decided to spend some time watching Tamarins playing with each other. Jonathan was another guide we had a wonderful, very knowledgeable, and fun time with. We honestly just didn't want to leave and wish we could have stayed longer. Nearby activities: We did the macaw clay lick, mammal clay lick, night walk, medicinal trail, canopy walk twice, and the oxbow lake. Safety: As safe as you can be in the Amazon rainforest Food & drinks: Excellent varied buffet lunches and dinners every day. Read all
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