<img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=1691026687882470&amp;ev=PageView&amp;noscript=1">

Rainforest Expeditions Blog

Mystery of the Yellow Bulbs: Discovery in the Amazon of a New Caterpillar-Ant-Parasitic Plant Relationship

[fa icon="calendar"] Nov 29, 2015 9:00:00 AM / by Aaron Pomerantz

Aaron Pomerantz

“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...

 

 

Watch the video 'Mystery of the Yellow Bulbs: Caterpillars, Ants and Parasitic Plants.'

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

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.

2_Closeup_Bulbs_on_Bark.jpg

 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 on to 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.

3_Caterpillar_Eating_Bulb.jpg

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.

4_Caterpillar__Ant.jpg

 An ant, Ectatomma tuberculatum, guarding a caterpillar
 
5_Caterpillar_Ant_Finger.jpg
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.

GIF_1_Cateprillar_Ant.gif

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 a 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!?

6_Butterfly_on_Tree.jpg

A butterfly with a yellow wing spot lands on the tree

Ok, Homework Time

I wrapped up my field work 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 tree with yellow bulbs


I assembled the photos from the trip and starting 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.

Caterpillar_young_and_ant.jpg

 An ant protecting two young caterpillars

With the help of some experts, we were able to identify the butterfly as Terenthina terentia, which belongs to 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 this criteria.

me_filming_yellow_bulbs3.jpg

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.

7_Tree_bulbs_2.jpg

The yellow bulbs later identified as a rare flowering parasitic plant

Jan_2015_Phil_image.jpg

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 described 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.
8_Caterpillar_Morphology.jpg
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!

 

-Aaron Pomerantz, Entomologist

You can follow Aaron for updates & get in touch on Twitter @AaronPomerantz

Terenthina_terentia_compilation.jpg

Special thanks to colleagues in and out of the field who assisted with this project, especially Jeff CremerFrank PichardoChris A. JohnsPhil TorresChristie WilcoxJason GoldmanTrevor Caskey, and Alex Gardels. Thanks to Andrew WarrenAlex 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 
 

Aaron Pomerantz

Written by Aaron Pomerantz

Entomologist and Rainforest Expeditions brand ambassador

Ever dreamed of discovering a new species?

At Rainforest Expeditions, our team discovers about 10 new species a month! We've launched a new project called Wired Amazon, connecting you with our scientists and their amazing projects. Learn more about Wired Amazon

 

Watch and vote for our film! 

 

 

Sign up for regular news from the Amazon